Gooseneck pin question for Dory Sloop mast boom

The manual indicates a 3/8" hole on the boom for the gooseneck.  Looking at the gooseneck it would seem 3/8" is too small and 1/2" should be the hole.  Is it indeed a 3/8' hole that I jam the gooseneck into?

 

Any clarification is appreciated.

Tim

   It is 1/2" and not 3/8" as stated in the manual.