There are two Benny Hill "Hell Holes" in the barrel which I believe are 3/16", the barrel is 4.9" so it's sort of a mid length bull barrel gun. I bought the comp used with the slot already cut in the top; from all the pictures I've seen of these comps, some have holes in the comp, some have slots, but they all seem to incorporate at least some barrel ports. This one looks like it has seven holes in the barrel plus the slot in the comp: