Fits all 4speed Big Twin frames from 1970 thru early 1984, and is available in two different versions. One version has a 2.44:1 closeratio first gear with a 1.35:1 close ratio third gear, which is an ideal combination for FX models. The other version has a 2.60:1 close ratio first gear with a 1.35:1 close ratio third gear and is ideal for FL models. The shifter clutches and shifter dog faces are widened .020" to prevent chipping. The transmission cases are machined from 356 aluminum alloy castings that are heat-treated to T6 and have been clearanced to accept belt drive pulleys. Included is a set of speedometer drive gears that will drive 1:1 ratio speedometers. Transmission sprocket and clutch arm are not included, these must be ordered separately. Perfect for those of you building new bikes, or replacing your original transmission that's left you on the roadside just once too often.