The MFF-1 gives you Arri quality for 15mm lightweight setups. It's easy to mount and adjust, and has adjustable hard stops for use with lenses that have infinite rotation focus rings.
The gear mechanism is reversible for use with lenses such as those from Nikon.
The focus gear is a 6mm, 43 tooth, mod 0.8 variety. A rubber friction gear is also available to make it possible to use the MFF-1 with stills lenses without the need for lens gears.