this is definately a commercially made oval insert..not custom...
he had a whole display of them....it is oval from top to bottom, you can install it either way and it feels the same.
For my thumb it is a PERFECT fit, I just want to get more of them...
In the smaller sizes it is a 1 1/8" drilled hole, when you go over like 15/16 it becomes a 1 1/4" hole...
the link to bowlers paradise looks like it, but that says "oval on one end, tapered on the other"
?
I'm going to call around today and see what I can find...