Open and close your watch case backs with this simple, yet highly effective 65mm rubber friction grip ball. 

The ball should not be fully inflated to work efficiently, the softness and slight 'give' in the ball will allow for more grip.  Hold the watch in your fingers and squeeze the ball, allowing the pressure and slight stickiness of the ball to open the screw case back. 

Will not mark or scratch. Wash the ball from time to time to keep the ball working efficiently.