This Mister B Stainless Ball Stretcher is made of hi grade stainless steel and opens with a hexagon key which is included with this product. All the edges have been carefully smoothened, and polished to perfection, it is relatively easy to put on without catching or pitching of the skin.
It may be a bit old skool and clumsy to have them with a screw, but on the other hand: if the size is right, these never fall off once applied as opposed to the magnetic ones. 34mm also available.