The Ruff Rider callus builders fit perfectly onto a grip master hand strengthener. The do not slip or move in any way. They are very coarse and will build calluses on your finger. Great for musicians. My only problem is that they do not fit over the 11 pound grip master pro. They are much to small. If you you plan to use the two together, forget it. Other than that, this is a great product and you will not regret buying them.

Simply put, these caps coupled with a Gripmaster are an easy and effective way to build and maintain callouses.

I started playing guitar 3 months ago. I work in an IC fab where we must wear plastic gloves for hours on end. The constant heat/moisture inside the gloves softens any calluses quickly. I bought these for use on my blue gripmaster and have been 100% satisfied. I had good calluses after about a week and am able to maintain them with minimal daily use. I'm able to practice guitar as much as I want, (but probaly not as much as I need...). They work, they're inexpensive. Buy 'em.

I got my heavy gripmaster before I got the grip caps and thought it wouldn't do anything. I was wrong. I put the grip caps on and suddenly I can't just crush and hold the gripmaster. I am also a shooter and the gripmaster is supposed to help with trigger control too. I'm sure it helps with guitar fingering. I can hold my strings with relative ease. Now all I need is to learn to play it like a pro. I would definitely recommend this product to guitar players. It's incredible!!!!

Very secure fit on the Gripmaster. Used with the light tension (blue) Gripmaster it was painful for the first few days, but I had noticeable calluses after two weeks and now after one month, they're quite significant (I can hardly feel the keys as I type this). I use mine a lot, while driving, walking and watching TV, and they have improved my guitar playing.