A trim wedge for your rudder. Material is PET-G that is resistant to acetone, paint thiners and fuels. Proseal would be a good adhesive choice to use to bond the trim wedge. The hollow versions are 40% lighter. Based on what I have observed over the years, .300 is the typical aft thickness. ( I personally use .275 inch. x 1 inch x 4.0 inch long but each aircraft is different. ) To resist UV rays, a coating of UV resistant enamel paint can be applied.
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.