Applicable Scenes: Ergonomically designed to fit small to large hand sizes. perfect for men, women, seniors and teens. Fine workmanship and perfect style. Built-in button cell, if you keep exercising for 3-4 hours a day, the battery will last about a year. Great hand strengthener for musicians including drummers as well as guitar, piano and violin players. Design for athletes and sports enthusiasts who want to increase their hand, wrist, forearem and finger strength for rock climbing, , bodybuilding, golf, tennis etc. Colour:black Material:Spring steel+PP+ Size:17 x 12.6 x 2.6cm Package Contents: 1 x Grip strength trainer Only the above package content, other products are not included. Note: Light reflection and different displays may cause the color of the item in the picture a little different from the real thing. The measurement allowed error is +/- 1-3cm.