SECURE YOUR BIKES WITH EASE - Quadratec's bike rack adapter bar for bike rack connects to your bicycle seat post and reaches across to the handlebar stem to provide a safe and secure top tube for hanging onto a bike rack carrier ADJUSTABLE FOR A PERFECT FIT - the telescoping design of the bike rack bar accommodates most standard sized adult and kids bicycles and can be adjusted from 23.6" to 31.5 inches. It can support bikes weighing up to 33 lbs QUICK-RELEASE BUTTONS - the bike rack bar adapter is is spring loaded and features quick-release buttons that provides an easy load and unload process that takes only seconds ROCK-SOLID AND DURABLE - the vinyl coated clamp on the bike crossbar adapter protects your bike from marring and scratching, and the bike cross bar adapter's satin black powder coated finish ensures years of hassle free service FITMENT NOTES - the bicycle cross bar tube adapter works on bikes with a seat post diameter of 1.185" or 30.1mm or less, but will not fit larger seat post sizes 30.8mm and 31.6mm