Surepromise Watch Back Closer Watchmaker Press Set Repair Tool w 9 Alloy Press Stud To install bezel rings, friction inserting mineral crystal or battery changes. Perfect for changing batteries, bands and minor repairs on watches. Great for closing your snap back watch case after resizing or repair job. It comes with an assortment of 9 dies to allow for different size watches(19,21,23,25,27,29,31,33,34mm) Straight wall alloy dies will not scratch or mark.