I bought this when I handed me the bass after a year without touching, I lost a good part of my endurance, and I know how long it is to form hands on his instrument, the gripmaster is an excelent addition to direct training on the instrument, it allows to work each finger individually and offers a wide variety of position, in contrast with the extra heavy gripmaster its resistance 5kg really hefty and it takes a sacred fist to work each finger, so it's not that I hesitated just ordered my version 2kg of resistance for a progressive training.