We got a fully assembled 4.88 Offset Ratio third member from JTS Justdifferentials with no setup necessary. The Offset Ratio is for 4.88 or 5.29 gears. The company offers two other third members: one for 3.73- 4.56s and another for 3.15-3.58s based on the bore of the pinion bearings. It came in a box filled with nice nesting material padding and already had the rear ARB Air Locker installed and a super-clean pattern on Nitro Gear & Axle 4.88:1 gears. Installation was as simple as dropping the new third member in the housing, tightening the bolts, and installing the axles. In short, stupid easy.