This is the one cleat to rule them all. Shimano pedaling Dynamics, shortened to SPD, has long been the standard for clipless pedal systems since its conception in 1990. Hugely popular in the spinning classes of the world, the SH51 and SH56 are the most versatile cleats on the market. The difference being that the SH51 will only release by rotating the heel outward and the SH56 will disengage in either direction. For this reason the 56 is preferred for spinning classes and novices who aren't as comfortable clicking out. Technically a mountain cleat system because the small size of the cleat can be tucked away from the tread allowing for an unobstructed walking sole surface, these cleats are still ridden by many road cyclists and commuters for the benefit of an unhindered walking shoe.