Seat post shim, inside d. 27,2mm, outside d. 30,2mm. Material AL6061.where to buyphotogalleryproduct options Photogallery Product options silverd.27,2/ 30,2mm = UA#29911421 d.27,2/ 30,4mm = UA#29911441 d.27,2/ 31,6mm = UA#29911461