One of the few common complaints among owners of the Toyota Prius model NHW20 (2004-2009 model years) has been an ergonomic one: inadequate legroom and thigh support for tall drivers. I am 6’4”, an owner of a 2005 Prius for 3½ years. I have considered driver’s seat comfort only fair for extended highway driving. I keep the seat as far back as possible, which provides adequate clearance between the dash and my knees. But I can’t stretch my legs as far as I would like, and because my legs remain moderately flexed I end up with insufficient thigh support. An Obus Forme seat support makes things modestly better, but I have often wanted the ability to adjust the angle of the seat bottom or move the seat further backward. (The Toyota Corolla has a simple mechanical seat bottom angle adjustment. Why can’t the Prius?!) I have considered various aftermarket or home-grown seat modifications described on PriusChat or elsewhere, but cost, installation challenges, or potential safety issues have kept me from acting. When the ExtendMySeat Prius seat extenders were introduced, they seemed like an option worthy of investigation. This review describes my experience with installing and using the extenders. As of this writing, the extenders have been installed for approximately six weeks. Installation (The pictures I have here are not of the entire installation; they only call attention to my particular observations. For pictures of the entire process, I will refer readers to the excellent documentation on the manufacturer's web site. ) The extenders look solid and well made. The four bolts that accompany the extenders also appear solid, with the shanks approximately the same diameter as the factory bolts. Installation instructions are straightforward and easy to understand. The pictures in the hard copy instructions and the video on the product’s web site are quite helpful. As the instructions state, the only tools needed are a 9/16” socket wrench and 9/16” open-end wrench. A 13 mm socket would have been nice to have, but as the instructions suggest, the 9/16” wrenches work on the 13 mm factory bolts. Front seat removal was easy. The “A” extender (left) was installed first and attached easily. The “B” extender (right) gave a little trouble. The rear edge contacts the carpet (blue arrow), at which point there is a little “give” in the carpet where it is stretched taut across the bottom concave curve of the rear floorboard hump. The factory bolt (red circle) on this end points sideways rather than downward, so moderate sideways pressure on the extender (red arrows) is needed to compress the carpet and push the extender close enough to the bolt hole to thread the bolt. Between the angle and the small surface available to apply pressure on the extender, I found this a little awkward to do by myself and I made several attempts before getting the bolt threaded. A second pair of hands would have been helpful. After placing the seat and trying to align the seat rail bolt holes with those on the extenders, I encountered another small problem: the front bolt holes didn’t align precisely. I attached the left front first and then found the right front offset as shown here: I tried to manhandle the seat to bring it into alignment with no success. I considered the possibility that the rear seat rails weren’t seating properly against the extenders, so I unscrewed the left front bolt and attached both rear bolts. The fronts still didn’t line up perfectly. (The picture actually was taken after the rears and left front were attached.) I manhandled it some more and finally got it aligned enough to thread the bolts. Some assistance here again would have been helpful, though I suppose there could be a small design flaw. I am interested in hearing others’ experiences with this. All bolts were tightened and electrical connections reattached. I replaced the rear floor mat, removed for installation. This shows the mat in place and covering most of the rearmost part of the right extender. The mat does not cover the left extender because, as may not be apparent here, the tip of the extender is raised off the floor by an inch or so. I probably could have wedged the mats (both the factory mat and a clear vinyl ExactMat) beneath the right extender, but I wanted the mats to cover it. My only aesthetic complaint is the visible left extender, but that seems unavoidable. Total installation time was a little less than an hour. One lingering question I have is the torque values that should be used for the bolts. I would assume Toyota’s torque recommendations can be used, but they are not included in the instructions. I needed strong arm pressure and some leaning into the 10" wrench to loosen the factory bolts, so I tightened them with what I guessed was the rough equivalent. I’d feel more secure about such critical attachment points if I had correct torque values. Driving Impressions Simply put, the extenders accomplish their mission. I now have substantially more legroom of course, and I can extend my legs enough for the seat to mostly support my thighs. (I say “mostly” instead of “completely” only because my thighs extend beyond the seat.) Only problem now is that I need longer arms! With the seat in the rearmost position I have to lean forward to get to the EV button or the MFD. That’s a small price to pay, and it’s easily compensated for by moving the seat up an inch or two. That’s still substantially better than before and I can now choose from several different seat positions. I've found myself leaving it a little further forward early in my drives as I frequently activate EV mode and then move it back a notch or two after the car reaches S3/S4 operating temperatures. On longer trips I’m sure I’ll be making occasional adjustments to reposition my legs. It’s nice to have that option now. I've needed to adjust my arm position while holding the steering wheel. I typical hold the wheel at the 10 and 2 o’clock positions. Still wanting to rest my elbows on the console and door armrests brings my hands down to the 4 and 8 o’clock positions, something that I still am getting used to. I’ve never given much thought to a telescoping steering wheel, but it would be nice to have one now. I activate the window switches by feel, and early on I found myself adjusting the rear windows by mistake instead of the fronts a couple of times. I have since adjusted for that. The real test will be an extended highway trip. I have found previously that I need to stop every hour or two to stretch my legs while on the open road. I have done a couple of relatively short (1 hour) trips since installation, but I have no long highway trips (two hours-plus) planned until late September. I will update this review then. With both tall and short people driving a particular car, there is a concern about whether the short ones still can drive it with the extenders installed. My fiancée is 5’1”. She doesn’t drive the car, but after installation I had her sit in it with the seat all the way forward. She had no problem reaching the pedals, and she and others of similar height or leg length should have no problem driving it. A potential safety issue for some is whether the extenders move the driver back far enough to compromise the effectiveness of side air bags. I can’t evaluate that, but given that I don’t have side air bags, it’s not an issue for me. The ExtendMySeat Seat Extenders are available through the PriusChat Shop for both the driver's side and the passenger's side for $195 a piece, or $295 for the bundle.