Pull rivet drill bit size?????

Those are aluminum rivets and they easily remove form the top. We like top use a long nose vise grip and grasp the heads, pulling them out. The drill bit is a number bit under 3/16″ but we dont recall the size. The rivets are custom and probably only available through BCB.

The rub rail can loosen, though it is machine screwed every couple of rivets where the nylock nuts can be reached.