A Steering device is made up of two parts, the knob or grip which attaches to a clamp on the steering wheel via a quick-release pin. A bearing inside the clamp lets the knob/grip rotate freely. In other words, you don't need to change your grip, even if you turn the wheel multiple revolutions. The aforementioned quick-release makes it easy to change the knob or grip if desired.  

Knobs & Grips

Round

A popular shape for a Steering device knob is the spherical, aptly named Round. This knob is available in two dimensions small and large. The small has a diameter of 40 mm, roughly the size of a ping pong ball and the larger version has a diameter of 50 mm.

2-pin (tetra) and 3-pin (para)

Also known as tetra grip, these two let you hold the steering wheel like a handle. As they have the added benefit of allowing your hand to rest in the cradle, the 2-pin or 3-pin steering devices are good choices for those with impaired mobility or grip. The cradle is easy to reshape to fit the hand.