Optimist mast ring with a 45mm inner diameter, oval and conical shape. This oval inner diameter allows for maximum longitudinal play and minimal lateral play. The conical inner diameter allows for mast tilt. Four countersunk mounting holes. The diameter of the hole in the deck is 57mm. The Optiparts EX1210 is equipped with a separate sleeve that fits around the mast at deck level and protects it from wear .