This is an optimized gravity hook for towels. It can be easily mounted using double-sided tape. I added a ribbed wall inside the hook to increase friction, which allows it to hold items more securely. You can use any ball with approximately 16mm diameter, but for the best results, there is also an optimized ball model that includes an M5 nut inside. This nut adds more weight and makes it much easier to assemble the ball perfectly aligned (use superglue).