High quality High quality ABS wheels and mounting arms made of high quality steel. Our support arms for support wheels are 2.5 mm thick. For beginners this means more security and stability. Easy to remove Includes 2 x vertical bracket arms, 2 x wheels, 4 x nuts (2 nuts for replacement), go and enjoy your first outdoor biking exercise with your kids Safety design for heavy, solid bikes We attach great importance to the safety of our customers. The exercise bike added a small bracket that is more stable and helps young students ride bikes until they have a sense of balance on the bike. You don't have to worry about your children's safety. Universal & adjustable The stabilizers fit the single-speed bike inch from 14.12.16.18/20 with a horizontal fork end pointing backwards, but are not suitable for people with semi-horizontal or vertical dropouts. Cannot be installed on bikes with derailleurs.