This may not be necessary since the base of the mast won't be in the water during a capsize. And if it is you have more serious problems than water in the mast. If some water gets in the mast from the top of the pole during a capsize an unsealed base would drain water after righted. by the way: why are you replacing it? last thursday when I was 'sick' I went sailing instead of work(the conditions happened to be perfect). I was lowering the mast and one of the holes that the pin goes thru broke off. I am stilled pissed about that. It was a relative new $69 part. Do you h17 guys rotate the mast 90 degrees or 180 degrees when lowering the mast?