Speedmaster Large Cat Skeg Strut. These can be used on Catamarans of 40" or greater. Made with high quality aluminum, CNC cut to tight tolerances. Made in the USA! Includes: Brackets Strut blade Cross drilled brass strut bushing for .250 (1/4") prop shafts. Requires:.250(1/4") Strut requires K&S# 8133 5/16" brass stuffing tube.