A trim wedge for your rudder. Material is resistant to acetone, paint thiners, fuels and UV resistant. Proseal would be a good adhesive choice to use for permanent bonding the trim wedge. For flight testing, a vinyl or alum tape is good enough to determine final size. The hollow versions are 40% lighter. Based on what I have observed over the years, .325 is the typical aft thickness.
Note: the angled version is for RV's with a fwd angled rudder trailing edge. if you are applying the rudder wedge to a Glastar or similar with a aft angle rudder trailing edge, choose the opposite side (left/right) orientation to have the proper angle orientation.
Rudder Trim Wedge