Item : B0002H0N26 Customer Reviews Amazing by .. J. Mohorich (Sacramento, CA USA) These have given me great results with my time off guitar, my calluses grew fast. I use it with the blue grip master and keep it with me all around to work my fingers. The caps snap on secure and on the top the mimicked strings really bite into the fingers, for new hands it will hurt until the calluses get going. The more often you keep on it the faster the calluses seem to grow. Great Product! Does just what it says by .. J. Powers (Colorado) These caps fit on the keys of the trumpet-like hand exerciser and give the finger tips some toughening of the skin. My son uses it to maintain calluses for bouldering, but it would also maintain/create calluses for guitar playing, etc. Thanks. They Do What They Say They Do by .. Cerebellum () 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. Work Great by .. W. Mitchell (Virginia) Simply put, these caps coupled with a Gripmaster are an easy and effective way to build and maintain callouses. Builds and maintains calluses just as advertised by .. M. D Schneider (Corvallis, OR USA) 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.