I've done plenty of customers bowling balls, without any problems. The only problem I run into is getting the drill depth dead-on when doing a sleeve. Sometimes if a customer has a mix between old equipment that has been beat up and resurface vs NIB stuff, we have a problem. I'll just ask for the thumb insert and I can nail the depth every time.
As far as durability goes, they are top notch. No breaks yet, just make sure they don't drill too deep thru the slug! If you just *tap* the locking part with the bit, the piece is TOAST.
Myself, I use exactacated thumb molds. Used to use Vinyl ovals, then slugs, now this. It is truly awesome!
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Nick Smith ... A.K.A. Les Badderâ„¢
Brunswick -=- PBA 03-05
¡Viva la nación de Brunswick!