This is a totally new concept in bushing technology made of reinforced poly-propylene. These were tested by an independent laboratory and they are as durable as the current steel bushings but with these added values. 1. CA glue will not stick to them. 2. They will not transfer over to the blank causing discoloring. 3. They will not cause damage to the turning tool. 4. They have a built in wear indicator. These New Bushings will fit any pen kit that requires the 20A bushings.