The Bergeon 8007 rubber ball is a great addition to any work bench or watch tool kit. A friction ball that opens the back of most screw-off style watch backs. This squishy ball is slightly tacky and creates a large contact area that allows you to open the back easily. Guaranteed to not scratch or leave a mark on your watch, this tool is great when you want to open a back without the hassle of using traditional case opening tools. Size: 2.6" diameter (67 mm)