Pre-made thumb slugs to fit your non-round thumb! Those with "flatter" thumbs, this is the slug for you! Pre-made to fit your thumb without making hardly any changes! Comfortable and consistent release! The Pro V2 is the popular "Box Oval" shape made with a vinyl material preferred by Pro Shop Operators.
I have tried it pretty much all. These are fast and easy to use.
I find the box ovals make it easier to get a snug thumb hole fit without hanging up in the ball.