It does not make the thumb slick. If you use a piece of black tape in the front side of the hole it can vary what you get. If you use regular bowlers tape it can be normal feel when you start but can cause you to hang up a bit if it gets warm. I use Valentino's Franken tape so that I never have a problem with hanging up, if my thumb heats up. I put it on the front side and I get the same release very time. Some balls have naturally tacky insides as do some thumb slugs. Valentino's Franken Tape makes it feel right every time without changing the pitch or size much at all.