I didn't make them then and don't make them now, but It was kind of a special case, and I made a double extension one time that was really long, and didn't want the flex of the rubber between the extension, and butt of the cue, so I used a uni-loc pin in the extension, insert in the end of the butt. For the bumper I cut a jump pin down, mounted it in the rubber bumper, so basically You just screwed the bumper off with a couple of turns then screwed the extension on. I think with the type of bumper shown, I could have just bored a recess in the extension face to except the back of the bumper and still achieved enough face to face contact between the end of the butt and front of the extension to keep Me satisfied though.