Works very well, easy to place and adjust without having to damage the guitar.
My Sister and I both play Bass (and guitar), I have
Big hands and hers are small, so the Thumbfin works awesome for both of use because we share all of our equipment!!!!!!
Using on a Hofner 500/1. The pickup position doesn't leave a lot of room to rest the hand. The comfort and playability are much improved with the Thumb Fin. Would give this product a 4.5 if able. Will consider addition for other basses.
Maybe explore some optional colors - black, white, silver?
If you can't find a suitable place to rest your thumb, this gives a very single and effective solution. Easy to move about and cash be removed at any time, all without any permanent change to the bass guitar body