[Universal Diameter and Available Size]Still bothered by the fact that some bike training wheels can only fit one or two sizes of bicycles? That's okay. training wheels with bracket attached with 5 various holes can excellently meet your needs to mount it on bicycles with sizes: 12, 14, 16, 18, 20 inch. round and lovely appearance perfectly match each other, like a blue lollipop, bringing your kids a chromatic . (Note: Unavailable for variable-speed bicycle) [Thickened Wheel with Quality PU Material]We have been looking for silent and hard-wearing bike wheels, especially those also can play a role in shock absorption. This training wheel made of quality PU material just fits that bill. Meanwhile, thicker wheel with 2.5cm thickness (0.5cm thicker than ordinary one) can reduce bumps and make for an easy with less effort and more comfort [Double Bearing and Larger Washer]After optimization, the double high carbon steel bearing of training wheel has been tested to be silent and , with wheel life. In addition, we have specially enlarged the washer so that it can cover the whole bearing nicely. So even after your kid has ridden for a while, you 't have to worry about the sudden drop of the bearing, which may cause your child's sudden falling to ground. safely and grow up freely [Thicker Bracket, Stronger and More Durable]Have you ever encountered a deformed or even broken bracket of a training wheel? 't worry. With that in mind, we designed a training wheel with bracket at 3mm thickness which is 20% thicker than regular one, exerting a stronger support capacity. Thus, it's not deformed or broken. Your kid will be with while luxuriating in learning to a bike [Easy Installation] equipped with wrenches, the installation can be completed. The locking bra is of an assistant for securing the bracket and bicycle. Couldn't be more simple! Meanwhile, we recommend the wheel should be about 5mm from the ground when the bike is standing , which is conducive to your kid's mastering the sense of balance in riding Colour: Black Material: plastic Package Contents: 2 x wheels 1 x wrench 2 x screws and nuts 2 x cushions Only the above package content, other products are not included. Note: Light and different displays may cause the color of the item in the picture a little different from the real thing. The measurement allowed error is +/- 1-3cm.