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. Built-in button cell, if you keep exercising for 3-4 hours a day, the battery will last about a year. Design for athletes and sports enthusiasts who want to increase their hand, wrist, forearem and finger strength for rock climbing, , bodybuilding, golf, tennis etc. Great hand strengthener for musicians including drummers as well as guitar, piano and violin players. Applicable Scenes: Ergonomically designed to fit small to large hand sizes. perfect for men, women, seniors and teens. Fine workmanship and perfect style.