I just built a custom wrist wrench to train for the inch dumbbell. I heard a few of the people in the community say that the wrist wrench helped them quite substantially to train for the inch dumbbell. The handle is slightly bigger than the RGT from Grip Genie. Which I believe is 2 3/8 just like the inch. The grip that I have is very slick which I hope gives me a predisposition so when I give my inch trainer a lift makes it feel way better because of the texture difference. Let me know what yall think and which wrist wrench’s you all use!