[Seacraft84]

It is 3". I sanded all the high pieces of glass that were in the way. It was a tight fit and you had to push it down in there. But I do not think with it being in there tight would cause any trouble. I put some cabosil on top of it, mainly because I had some extra. I also drilled about 6-7 holes in the bottom of it on each end in the event water got down inside it because it is not going to be sealed up at either end.