VOSAREA 4-Piece Dumbbell Bar Nut Set - Spin Screw Clamp for Weightlifting & Strength Training - Gym Equipment Accessories for Home & Commercial Use

They are made of plastic but they seem to be well made . I tested them pushing them with the weight plates on my dumbbells to see if they’d slide off the handle and they didn’t ( I used 15-20 lbs to test them ) . If they handle is held horizontally I wouldn’t worry about it but some exercises require holding the dumbbells vertically and that’s why I tested them to see if they would stay locked in place secured , they did . I’ll update if I end up having any issues . They get the job done .