DADDARIO (D'Addario) PW-VG-01 Vari Grip Stored almost without use. The following is quoted from a certain online shopping site: ■ Vari Grip ■ Hand Trainer ■ Adjustable tension for each finger. ■ The reversible grip allows for training individual fingers or overall grip strength. ■ The string-simulating parts allow for training to toughen the fingertips, preventing pain when playing guitar. ■ Pocket-sized and durable construction. You can practice anytime, anywhere, even without your instrument.