Topeak MTX Dual Side Frame Seatpost Mount Rack attaches to Topeak MTX BeamRack series in seconds.Tough 6061 T6 aluminum constructionAttaches to Topeak MTX BeamRack series in secondsPerfect for using Topeak MTX trunk bag with panniersEquipped with RX dual side frameAvailable V-type for big frames and E-type for normal framesSize (L x W x H): 11.6" x 0.8" x 12"Tough AL-6061 T-6 aluminum constructionItem SpecificationsColorSilver/BlackWeight300gFits Post Diameter25.4-31.8