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. 4 countersunk mounting holes. Hole size in deck: 57 mm.
The EX1210 has a seperate sleeve which is fitted around the mast at deck level and protects the mast from wearing.