For setting your engine proper deck height.
Use these shims to adjust deck height for optimum performance. No need to machine the pistons.
All popular thicknesses offered. 

Sold EA 4 needed per engine

Check out our engine calculator to determined proper thickness.

http://www.aapistons.com/pages/engine-capacity-and-compression-calculator

Sizes available: 

.010

.020

.030

.040

.060

.090