With this seat post adaptor, you can mount a rear carrier on bikes that don't have seat stay braze-ons (upper mounting holes).* It also allows your carrier arms to be lengthened to fit different size bikes or for extra heel clearance. Features Width adjustable mounting strap. Mount and straps equipped with non-slip, non-scratch pads. Carries up to 25 kg (55 lb) on Ibera carriers. Compatibility PakRak touring carriers, and most third-party touring carriers. Fits round, oval, and other odd-shaped seat posts and seat post sizes. Extender provides 55.2mm (2.17") extra length. Attach a carrier to bikes that don't have seat stay mounting holes. Seat post mounted.