By sandwiching it between the foil mast's top plate and the board, you can adjust the foil's base angle. You can adjust in the following 4 patterns by combining the two types of shims, 0.5° and 1.5°. 0.5° 1.0° 1.5° 2.0° Combining the 0.5° and 1.5° shims by swapping them front to back results in a 1.0° shim. Combining them in the same direction results in a 2.0° shim. Compatible with M6 and M8 bolts. Wing foil related items such as harnesses and leashes are listed below ⬇⬇⬇ #BCWorksWingFoil I also have other wing equipment such as harness hooks and belts listed. See my listings here ⬇⬇⬇ #BCWorksWingFoil Wing foil Wing foil wingfoil foil