The focus of this hub is finger stability and position awareness.
Place your thumb on the small upright plate that is fixed to the base. The fingers go onto the free spinning hub portion, where they will be challenged to keep it still during the course of the lift. The hub is connected to the base plate with bearings to allow a smooth and quiet spin.
It is recommended to train with a strict lift style (rather than freestyle) to allow for a more balanced improvement to the stabilization components of all the fingers.
The 3" is the most popular, given it's proximity to other commonly contested hub diameters.
By default, the finish on the hub (free spinning part) is kept to raw steel to support consistency in competitions and also to allow for natural seasoning.