Received this bike trainer on time, already mostly assembled and ready to roll. I only had to attach the feet and extend it to fit my mountain bike. It came with an extra band, which I plan to extend to a DIY rock tumbler for extra resistance.The spools are parabolic in the sense that the ends curve up. the central portion of the roller has been milled flat. It has a good grip on the tire. The bearings are of the quality that you can free spin the roller for a few seconds.It is very lightweight yet stable on the feet. The adjustable feet have soft bottoms to dampen noise and grip the floor. It was very comfortable to launch using the additional step pad. When not in use it can reduce in length with two twists of a butterfly nut, and I can fit it between the couch and wall.I highly recommend this trainer.Things you should know. It works with a MTB S and M frames with 29 wheels, however you have to fully extend it. It has two rubber bands, one already installed and a second spare one. There is very minimum assembly required. I'm a first timer user so it took me some time to find the balance however I assume this is regardless the described item. Construction material seams to be well done and durable.It doesn't feel good is really weak it feels that it wants to brakes i returned and sellers give me the hardest hard time ever ,I'm never buying anything from this person ever