Topeak Beam Rack Seatpost Mount Rack constructed of tough 6061 T6 aluminum.Tough 6061 T6 aluminum constructionHinged seat post clamp with aluminum quick release leverPerfect for mountain and trekking bikesFits 25.4-31.8 mm seat postsCarries 20 lbs and loads with easeItem SpecificationsColorBlackWeight680gRack Weight Limit20lbsRack Length9insClamp Height32mmFits Post Diameter26-30mm