This tool enables quick, accurate quartering of drivers up to 1" O.D. on 1/8in or 3mm axles. The wheel is located onto the axle while the wheelset is securely held in the tool avoiding possibility of slippage. Can also be used to compare quarter of existing driver sets. A .100in clearance is required on each side of the gear. Will not fit drivers with gears wider than 1/8in (most drivers have narrower gears). Will not fit most Rivarossi drivers due to inconsistent axle diameters. Operating suggestions included.