This Bottom Bracket to compatible with 68/73mm BB shell and with both Shimano HTII & Sram GXP via the aluminium adapter shim which is supplied F.O.C. with each B.B. + 2x Spacers. HTII USERS. You will find a shim (silver) located in the clear spacing tube, you will not need to use this shim, it is only required for GXP conversion.