These Skulls can be used for Knobs or Encoders. They work great on the Reloop Spin and PTO1. They fit 6mm D style post, Use them as a Pointer knob the head is degreed to your order and points to the 12 o clock position on you .gear. They also make perfect Encoders! All products use our patented sleeve for a perfect fit. These product’s are built to order and come with knob lifters tools.