The new distributor from Rock Auto comes with this pin in it. We’ve never had a problem slamming a distributor in a 4.0L HO engine. However, this pin keeps the distributor pointed at number one cylinder. Since there is a fork where the bolt goes through, if this pin is in, the engine is at TDC, and the bolt goes through the distributor you know for sure the distributor is in correctly. It just shears off when you crank the Jeep the first time.