Years ago a doctor told me that my left leg was slightly longer than my right. I never really noticed that this could be a problem until I changed saddles from an SMP Glider to a Specialized S-Works Power. The Power being a flat saddle allowed me to slide over to the right side in order to compensate for the leg length difference. something that was not as easy to do on a ridged saddle like the SMP. I experimented with the shims starting at 3 MM and finally ended up with 6MM of shims under my right cleat. With these in place I sat squarely on the saddle, and it proved to be the most comfortable saddle I had ever ridden. These were well worth the price as they corrected a long extant problem. With things evened out, it was far easier to find a correct saddle height as well.. I should note that these are designed to work with Shimano road cleats only.
I have tried a number of lifts to correct a leg length discrepancy, but they were all designed to work with multiple pedal types. As a result they never worked really well with my Shimano cleats. These spacers are designed to work with the Shimano SPD SL cleats so they work very well. And the price is right!
One caveat though. I needed a full centimeter of lift (two sets worth) so I had to locate my own mounting screws.
The product worked like a charm. Good solid materials, stacked nicely. It didnt slip when I really cranked down on the bolts for the cleat. Highly reccomend this if you need to level out your leg descrepencies.