The 6 mm setting punch is meant to help close 6 mm Tube settings. They are calibrated to fit a setting that will hold a 6 mm stone. The inside is convex to sit over the stone and keep it from breaking while applying pressure to set the stones. I like to use the settings from Halstead bead as they have a slightly thinner top wall that folds over the stone just beautifully. I really like the longer shank on this as it makes it easier to hold and keep my hand steady and stable while setting the stone.

https://youtu.be/tiulsf9iVd4

NOTE: This is a pre-order. I have to custom order these punches. I do not know the exact timing on getting these into stock. But I will keep you posted as soon as I have them in my hot little hands.