Original Shimano MTB SPD cleat available in 2 models -

• SH51 SPD single release cleats, recommended for all MTB SPD pedals except PD M858: release the cleat by twisting heel outwards. In layman's terms, this is the cleat that will fit 99% of SPD compatible pedals.
• SH56 SPD Designed to work with all open design pedals: allow your shoe to be disengaged by rolling or twisting the foot in any direction.