The long and short of it.
Leg length discrepancy is one of the biggest issues in dialing a bike fit, but the meticulous tinkerers at Speedplay have the solution. The Walkable Cleat Leg Length Shim Kit compensates for the shorter member of the pair, evening the pedal stroke for a more uniform feel. The kit includes two 1/8in shims and the necessary mounting hardware, and is only compatible with Speedplay's Walkable Cleats. Note that it doesn't include the cleats themselves.