Kevin from what I remember they bosses are cast for the twist in style breather. But you might be able machine them for press in i'd imagine. I'm working out of state and don't have them handy. I'll have my son take some pics inside and out of each for you and Ernie. Sorry bout the delay. I bought them from Barry R at Survival. If you go to his site
www.survivalmotorsports.com and click on the BT images you see the as cast finish. They are the set I bought and Barry snapped a pic for his site before shipping them to me. Overall I'm very happy with them. I had a set of the FMS polished "Cobra LeMans" covers before these. They were made for twist in breathers also. Same thing only the sides were polished and I did the tops myself. There was a bit of casting slag between the fins to cleanup also. I think the BT covers are cleaner in this area and have an overall better appearance.
G.