You’ve decided you want an underseater. If you’re like me, you’ve been searching high and low trying to figure out if any of them will actually fit under a seat, reading scads of reviews and comparing published bag sizes to airline restrictions. And if you’re like me, you’re exasperated, finding that the listed dimensions of the same bag will have 3 different measurements depending on the website you’re looking at, and are about to give up. Maybe this’ll help. I’ve tried 6 of them and this is how they stack up.Here’s why I started looking for an underseat bag: I wanted to replace my purse. I always travel with a checked bag and personal item. And I am done carrying a 10 lb bag on my back or shoulders. I am done carrying anything at all.I frequently fly between the US & Canada. This trip requires traversing 3 airports and many pedestrian miles, including going up and down stairs, and standing in long lines at customs as well as security. And because, well, Canada, I’m usually doing this in a heavy parka. I’ve made this trek carrying tote bags, backpacks, crossbody bags, and purses. I’m no spring chicken, I have some medical issues that affect my strength and stamina, and I am done carrying. Anything.I wanted a purse on wheels – and not on 2 wheels, but 4. Cue the search for an Underseat Spinner.I compiled a list of Personal Item maximum dimensions for every domestic and Canadian airline I could find. Comparing that data to most of the Underseater Spinners on the market, it was clear that there is, in fact, is no spinner bag that will fit the requirements of all airlines – especially the 2 I fly most frequently: Air Canada and United. But there are some that will fit under some seats and I still wanted that option.After testing a few underseaters I accepted that on most flights on most airlines I’d have to put my bag overhead rather than underseat. I thus adjusted my priorities: I wanted the smallest bag I could find that would roll beside me through corridors with ease, a solid handle that pops into place and retracts without effort, and a sturdy grab-handle that I could easily grip when going up and down stairs. I also accepted that I needed to double my initial $100 budget. (And eventually realized I needed an additional bag for my Personal Items, which I address at the end of this tome.)Items 1-3 can be found for under $100. The Samsonite Lineate/Silhouette can be found for well under $200. The 2 Hartmanns I bought for right around $200.I’ll also note that as I went through the testing period, a built-in USB port became highly desirable. Either you want one of these, or you don’t, but none of the bags listed here come with a battery pack – just the port. So if you won’t use that feature, it doesn’t take up any extra room and you can use the dedicated pocket for something else – or leave it empty.Here are the ones I rejected:1 - Aimee Kestenberg Women’s Florence 16” Polyester Twill 4-Wheel Underseater Carry-on This is the smallest bag I tried and would probably fit underseat on most airlines. It is a true Purse on Wheels. But the handle is poorly built and so wobbly that the bag constantly tipped and wouldn’t roll in a straight line. This was true whether full or empty. The zigzagging motions of the bag jerked on my wrist and after just a few tests in my apartment, my wrist and hand were throbbing with pain. This bag has a built-in padded tablet sleeve that is too small to fit my Surface 6, even without the cover (Surface Pro 6 dimensions are 11.5” x 7.9” x 0.33”) which meant that the empty padded sleeve took up a lot of unused space in the bag. This bag is cheap, cheaply built, and I wouldn’t expect it to last long.2 - Samsonite Underseat Spinner II with USB Port This bag had the same problem – the handle is flimsy and loose. I rejected it fairly swiftly for that reason, and didn’t bother checking to see if the issue was rectified by packing it (heavy stuff at bottom, etc.) This was the 2nd smallest bag I tried, as far as the case itself, coming in at about 16.5” x 13.5” x 8”. EXCEPT for one very important thing: the wheelbase protrudes beyond the edges of the bag, making the bottom of the case 14” x 9”. Would that make any difference shoving it under the seat in front of me (these bags are generally designed to slip under the seat handle first, with the wheels facing out)? Hard to know until you try.I compared this bag to the Samsonite Lineate/Silhouette (discussed below.) Without measuring, I could see that both wheelbases are the same size. However, the Lineate/Silhouette case is substantially larger with a wheelbase that’s flush to the case. I’d be hard-pressed to understand choosing a smaller case over a larger one when the wheelbase is the same size, except to save money. This is the cheapest bag I tested and costs about 1/3 of the superior Samsonite, and beyond that, I can’t see any reason to buy it. It also has floppy nylon webbing carry-handles that hang on the sides. This seemed smart (inasmuch as they’re not going to take up any extra space) until I tried to get them into my hands with a firm grip. It just takes too much work (i.e., time), and I knew that would ultimately be frustrating. In fact, to remove this suitcase from the box it was shipped in, I had to turn the box upside down and shake it out since there’s no grip-handle on the top of the bag.3 - London Fog Cambridge II 15" Wheel Underseat Bag From my aesthetic perspective, this was the best-looking bag I tested, and I was initially willing to overlook its downsides for that reason. This bag is much bigger than advertised, coming in at about 17” x 16” x 9”, and is in fact is the largest bag listed here. That said, the way it’s designed makes it awkward to pack and thus it does not have the largest capacity. The front pockets are flush to the bag, rendering them essentially useless. It also has a somewhat domed top, which is just poor design, as that’s where the (non-removable) tablet sleeve is. That means you’ve got a hard, angular item under a curved cover. It’s inefficient and, for me, resulted in a lot of wasted space.But the real dealbreaker is the handle. The more I played with this thing, popping it on and off my checked bag, lifting the trolley handle and rolling it around, the more difficult it became to lock the handle into place. As in, sometimes it just wouldn’t.One caveat: I’ve occasionally found myself having to travel with a 15” HP laptop. I tried to fit the laptop in all 6 of the bags listed. This is the only one it slipped into easily, albeit on the bottom of the bag laying flat under my other items. It didn’t fit in any of the other bags except the Lineate/Silhouette, and only then at an angle. Were I planning on traveling with a 15” laptop on a regular basis, none of the bags reviewed here would do.4 - Hartmann Metropolitan 2 Underseat Carry On Spinner This arrived along with the Hartmann Herringbone Deluxe Underseat Carry On Spinner discussed below. On unpacking, I found the Metropolitan 2 to be just slightly bigger than the Herringbone, so it had already lost out based on that comparison. More than that, however, after just a bit of messing around, I knew that the zip-around flap covering the pull-up handle was going to drive me crazy. It’s a nice touch and gives it a bit of a luxury feel, but just a few times of trying to get to the handle made me irritated enough that I knew it wasn’t going to work for me. This feature might be fine for a carry-on, and is certainly desirable on a checked bag, but I know my underseater handle will be extracted and retracted frequently, so it’s a problem. That said, if I didn’t already have some better-designed bags to compare it to I may have been willing to overlook this.This underseater is otherwise well-made, and my Surface 6 fit into the laptop sleeve with room to spare. The laptop sleeve, let me note, snaps out of the bag making it completely removable. I might suggest to luggage manufacturers that ALL computer sleeves be designed this way. It makes the bag a million times easier to pack, and in some cases, users might not want a sleeve in their bag at all. After playing with the case a bit, I found it to be solidly built with handles that snap up to multiple heights, which are covered in soft rubber that are comfortable to grip, and wheels that float like a dream.One of the reasons I bought 2 Hartmann underseaters is that their exterior dimensions varied wildly on the Hartmann website. Since they looked more or less identical online, I wanted to have both in hand to compare them. The Metropolitan 2 is, in fact, ever so slightly larger coming in at about 17” x 14” x 8.5” versus the Herringbone Deluxe, which I measured at about 16.5” x 14” x 7.75” (empty.) I’ll also add that my measured dimensions do not comport with Hartmann’s, which indicate that both underseaters are larger than what I measured on my own. Go figure.Runner-Up5 - Samsonite Lineate Underseat Carry On Boarding Bag with Spinner Wheels This product is also sold as the Silhouette 16 Underseat Carry-On Spinner. Gosh, this is a nice bag. I can’t say that I’ve ever been drawn to either the Samsonite name or aesthetic, but this bag has completely changed my mind. It is solidly built and thoughtfully designed. Like the Hartmann Metropolitan 2, the laptop sleeve is completely removable. It has a feature that none of the bags I tested share: the front pocket is both very wide, and zips all the way around then slightly under the bottom so that when unzipped it lays flat. It has an elasticized back slip pocket running the entire width that my Surface slid easily into – both with and without the cover. Brilliant! That meant I didn’t need and could remove the interior laptop sleeve which massively increased the usable space inside the case.The USB port is smartly set inside the top interior flap of the case’s cover. On the other bags listed here, the USB port is in a side pocket, making it both a bit awkward to access and creating a protrusion on the side of the bag.I tested each bag’s capacity (except the Samsonite II and the Hartmann Metropolitan 2) by packing it with the same items: LeanTravel size small packing cubes, a full TSA-compatible liquids bag, a 9” x 7” leather pouch containing my *Personal Items (discussed below), and my Surface Pro 6 plus its charger and a long USB phone cable. This case fit all of the above, with 2 of the small packing cubes stuffed to capacity, and left me with room to spare. Like lots of room to spare. Note that this is primarily because I didn’t need the interior laptop sleeve and thus removed it.When I packed this bag into its box to return it I was sorry to say goodbye. It’s a well-designed, well-made bag. If longevity is your top priority, this is the bag I would recommend. The fabric is high-quality, the handle and wheels are top-notch, it’s got a very solid sturdy build with reinforced corners and even a little hand slip on the bottom of the case to aid in lifting. It’s actually quite nice-looking – better in person than online, IMO. I like the color-match wheels and matte aluminum handle, which can be adjusted to different heights. I’m considering picking up the carry-on version of this bag.There is one downside, and it’s minor: the material on both hand grips. They’re covered in spiky rubber. I have a medical condition that makes my skin ultra-sensitive to rough textures and after a full day of traveling, I suspect it would cause a fair amount of irritation. But for the average person, this’ll probably be a non-issue (my husband, for instance, liked the way it felt.)6 - Hartmann Herringbone Deluxe Underseat Carry On SpinnerThe Unicorn.Even fully packed, this bag measures 16.5” x 14” x 8”. That means, according to the airlines’ stated restrictions as of this date, it’ll fit underseat on Spirit, American and Frontier. In a pinch, it might work on Southwest, and maybe (maybe??) Allegiant.This is not the best-designed or highest quality bag I tried. But it is an actual underseater, fits all my criteria, and is the one I’m keeping.The case is a little tippy when it’s empty. Packed full, it glides along without a hitch. The sides of the body have some flexibility and give, which given its use I’m considering a pro rather than a con. The body is polyester, not nylon and thus less durable, and the trim and top-handle are made of saffiano-look faux leather. (Since there’s no mention on the bag itself or Hartmann’s website of the bag having authentic leather trim, I’m assuming it’s faux.) Hartmann has a range of luggage from entry-level to luxe, and this bag is from the least expensive collection.*EDIT: I contacted Hartmann and they verified that the trim is indeed authentic leather.My Surface fits into the (sewn-in) laptop sleeve. It’ll fit everything I need. (Like the Samsonite, I fit 2 small packing cubes plus all of the stuff mentioned above and was left with some empty space.) The trolley handle is solid, comfortable to hold, and adjusts to different heights. The grab-handle pops up about 1” from the top of the bag, making it super easy to slip my hand in and lift. It’s easy to maneuver and pop on and off my checked suitcase. The front pocket is spacious enough to fit my *Personal Item pouch. It has a built-in USB port. It’s exactly what I’ve been looking for. Sold.[Aesthetically, I love the Hartmann vintage style. I got this in the black color and the herringbone pattern is quite dark – light & dark grey, though in some light it looks brown – and has a solid black extension handle and trim. It’s quite smart-looking on its own. Sitting atop my industrial-design Victorinox Spectra hardcase, there is a style clash. Oh, well.]Additional notes:*Personal Item Pouch: Upon realizing that replacing my purse with a small suitcase that in most cases will be stowed in the overhead bin, I realized that my purse needed a purse. That is, I’d need some way to access all of my personal items both walking through airports and at my airplane seat. For me, those items are: phone, passport, wallet, earbuds, small pillcase, lipstick, lip balm, compact mirror, hand cream. I have 2 compact purses I hoped would work, but both are structured with hard sides that are too fat to efficiently fit into any of the cases. I solved the problem by purchasing a flat, padded leather pouch that measures 9” x 7”. In some cases the pouch fit in the underseater’s front pocket; in others it only fit in the bag’s interior. In all cases, it’ll fit into an airplane’s back-of-seat pocket, making it quick and easy to slip into my seat when boarding.*I tested all of these bags atop a Medium Victorinox Spectra 2.0 suitcase. Because the underseater sits flush against the Victorinox handle, making it inaccessible, the stacked bags need to be guided by the handle of the underseater. The pull-handles of the pricier Samsonite as well as both Hartmanns anticipate this and have lock positions at 2-3” high, thus making it easy to pop the handle into place when it’s stacked on top of another bag. The cheaper bags did not have this feature (I didn’t test the Samsonite II.)*I tried my best to accurately measure each bag, but all dimensions are approximate. Because soft-sided suitcases are not square, they’re difficult to measure, and in most cases the dimensions change when packed versus empty. Measurements for the Samsonite Lineate/Silhouette, London Fog, and Hartmann Herringbone were taken when the bags were packed full.*I’ve not traveled with any of these bags nor did I test them in airport sizers. Therefore, their usability as true underseaters is based entirely on airlines’ published rules as of June 2019. YMMV.