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 use .275 inch. x 1 inch x 4.0 inch long. ) To resist UV rays, a coating of UV resistant enamel paint can be applied.