I was thrilled when these arrived in the mail. The price seemed unbeatable, and they fit securely to all of my standard bits. However, the metal in the hex screws is very soft, and after only 1 use the heads were completely stripped -- making these stop collars completely useless.I was using these in a fine woodworking application. But perhaps if you just wanted to use them as a guide for drilling into drywall, plaster, etc., then you could secure them less tightly to your bits (and thus, hopefully, delay stripping the cheap screws).