The Crossbar Substitute works as a top tube for easier rack mounting. For use with "hang-on" type car racks. Quick release clamps instantly adjusts to correct size for carrying "Y" frames or other unusual frames on common car racks. Sturdy construction with thick rubber coating to protect bike's finish. Distance between hooks max 30.32" min 21.25"". Distance from seat post to stem maximum 25.25-Inch and minimum 14.25-Inch.