The Optimist deck collar is made of Delrin to create minimal friction between the sleeve and the collar. The oval inner diameter allows the maximum fore/aft and minimum side play, and the tapered inner diameter allows the mast to be raked.SpecificationsColour: WhiteCountersunk mounting hole: 4Hole size in deck: 57 mmTechnical FileInstruction Manual .input-wrapper a { text-decoration: none; / Removes underline / background-color: transparent; / Ensures no background color / } .input-wrapper a:hover { text-decoration: underline; / Adds underline on hover / background-color: transparent !important; / Removes grey highlight / }