Potentiometer knobs with a nice grippy texture.

There are four internal sizes to fit most potentiometers : 

• standard 6mm diameter
• standard 6mm diameter with a deeper hole to cover the fixing nut
• larger 6.35mm diameter (often used on multi-turn potentiometers)
• larger 6.35mm diameter with a deeper hole to cover the fixing nut

The texture is inspired from the old G-clamp handle.