This is an entry-level bike roller, so the 4-stars are relative price/performance, and not relative to other more expensive bike rollers. The overall build quality felt good and solid to me, though the aluminum rollers feel like they wouldn't take much abuse. It came with a spare belt which is cool. Had the product arrived with the roller tension dialed in and ready, I would have given it 5 stars.Out of the box, this thing is not useable in my opinion. You must loosen the roller bearing tension, which as others have mentioned, is far too tight. The nuts required a 17mm wrench. You'll need to loosen the outside cap nuts first to gain access to the interior bearing nut. You'll want to loosen these as much as possible without leaving the nuts free to spin or introducing wobble in the rollers. Once these are spinning mostly free, re-tighten the outside nuts to secure the rollers. After that, you will want to place your bike on the rollers to examine the spacing of your front wheel. You will want your front axle to be directly above the front roller. The product is adjustable if necessary and there's a video associated with this product listing showing how that's done.Once the bike roller is set up, you're ready to get started. You'll need to find a level place where you can lean against a wall or hold something reasonably sturdy in order to start pedaling from a stopped position. A wall is better than a stool, since you can lean against it with your shoulder (not your elbow) and start pedalling with both hands on the handle bars. Start pedalling and try to gain balance on the rollers a little at a time. It doesn't take too long (15 - 60 minutes ?) to catch the hang of it but at the beginning it will seem impossible, as well as a bit scary. There are reasons for this which I discuss below, but if you're determined, you'll get there.Videos make it look easy, right? So why is it so hard when you're just starting out? Well, in a word.... momentum. You will have none and on a bike roller, you'll never have any. This is important because outside help we get from the gyroscopic effect of rotating wheels, momentum solves a lot of problems for you while riding a bike down the road. It allows you to take the road at your own pace, and keep the bike under you if you encounter a rough patch or trouble. There is a big departure from these things on rollers. 1.) You must keep pedalling in order to keep the bike under you. The instincts you developed to coast, and allow your forward momentum to keep the bike under you when encountering trouble will be of little use on bike rollers. On rollers, the lack of forward momentum means coasting is very unproductive at solving problems. If you run into trouble, you'll need to learn to pedal your way out of it. Adjusting your riding style like this isn't automatic. Though it takes effort, it comes reasonably quickly for most riders. Pain and fear make these lessons go quickly. It took me one hour and one broken closet door to get there but I made it. 2.) You can't take the ride at your own pace. There are no breaks unless you depart the bike. Rollers demand you keep the minimum amount of speed to stay upright on the bike. You may get good enough to slow it down but it will never be zero like it can be on the road. Every ride is continuously uphill. Because of this, be patient with how long you can sustain a ride. Two minutes doesn't sound like much, but it's a good goal if you're buying this to get back in shape and haven't ridden in a while. This sounds very short but with the amount of work you will be doing to stay upright and the fact that you can't coast, your heart rate will jump quickly and your quads will burn before you know it. So take frequent rests as you go. On the upside, because the work is in short spurts, I didn't notice much muscle soreness afterwards, despite disembarking from the bike with my legs on fire.Bottom line: this is an affordable way to keep riding, either in tight spaces or when weather is inhospitable to cycling. These are cheap rollers. My guess is, if can master these, better ones will be even easier if you decide to move up a model. There are obvious compromises which shouldn't be a surprise at this price mark, and they might be a little frustrating, but none of them prevented me from using the product. With proper expectations and persistence, you'll probably enjoy this product.Once the rollers were adjusted to fit my bike and tires inflated to max pressure, it worked great. The nuts on the rollers were over tightened from factory and I had to loosen them.Don’t expect to get right on the bike and start riding without falling, it takes practice and balance to ride sans holding on to a wall or a chair. I occasionally ride my bike on my treadmill so I was able to get on this roller with no problems.As far as work out goes, this is not an assault bike. You have to spin like the Tasmanian Devil to get a good sweat going. I’m sure there are a few tweaks I can do to get more resistance like deflating the tires and maybe tightening the nuts on the rollers(I don’t recommend that).*******Be sure to measure the wheelbase on your bike. I ride a 20” BMX, 26” dirt jumper and a 29er. My bikes are SM and I’m using the farthest hole. A bigger bike would not work with this roller.I’m gonna use this roller when the weather outside is not ideal. Turn up the volume to your tv or headphones, it’s not quiet. It doesn’t squeal like other reviewers have stated though. I recommend road tires if you’re using a mountain bike.Seems sturdy enough. I’ll update this review after a few months of use.It arrived to today (8/6/2022), I opened the box, read instructions, unfolded it and put my bike on it without making any adjustments. Works great so far. It is going to take some work to get good at riding on it. It feels like riding a bicycle on ice. I read a suggestion to put it in a doorway so you have something on both sides. Definitely a good suggestion.This is my 4th set of rollers, having previously owned Tacx and Cycleops.The main differences between RockBros and others is that each roller needs to be tuned when you set up. This because each roller has a nut on each side of the frame and sleeve between the two nuts. There is a 4th cross bar near the front rollers. It's a little extra work at first, but results in smooth and quiet rollers.Strengths:-The overall design and quality of components is very good, better than my Cycleops.-Very quiet compared to Tacx or Cycleops. I think some of this is due to the additional cross bar and the roller axle mounts.-The roller width is 17inches compared to 12inches. Not sure this make a huge difference but some might like the extra space.-Perfect height, when using on a rubber mat the legs are hight enough to prevent the band from rubbing on the mat.-Comes with wrenches and Allen key.Challenges-The additional cross bar needs to be removed when first installing or changing bands. This is a bit tricky as the Allen key that holds the bar screws into a plate that slides down the tube.-The band is a stiff plastic that goes on very tight and provides a constant resistance. I personally don't like this, I swapped the bands with a spare soft rubber band. I would use an external mag resistance device if I wanted a load on rollers.I would buy again.I place it close to wall and door frame in case I fall. So far I have been lucky and did not fall. It took 2 wks for me to build confidence using it without holding onto something. At the beginning it was difficult to pedal andI found it stiff so I had to stop and that is when you may fall. I think if the drums were larger it would have been easier but these ones do the job. Sometimes the bike moved right or left and I was afraid of getting off the rail.Overall, I think it is worth to have as I see good improvement in my strength and losing weight just by using it 15 min 3 times a wk. It is very light, compact and it easy fold and unfold.Title says it all. I blew out 3 tires in the span of 1 week in this.Also it costs $50 to return so if you end up not liking it almost a quarter of the cost will be lost upon returnGot this product a day earlier than expected, and is actually very good quality. My son loves it and it's great because it fits a 20" BMX bike, which most other trainers don't support. Great for training during the winter season.