HI,
Thanks for the reminder, JimmyB
BPEs or Bar Pin Eliminators are adaptors to convert the shock absorber mounts used by Jeep, and others, over to a standard type.
Jeep XJ lower mount at the front, and upper mount at the rear, use a modified ring as normally used on shockies ( the lower rear mounts are normal rings) fitted with a pressed in bush and integral bar pin. This Bar Pin is then bolted usually with two bolts to the body ( for the rear) or axle ( for the front).
Bar Pins means you have a limited range of shockies to pick from, the bushing style tends to wear and rattle. BPEs bolt to the old Bar Pin holes and allow a shockie with normal compression style bush ( like lower rear XJ, but usually bolts through rather than uses a stud). Since the bush is in compression it doesn't tend to rattle and can be easily replaced.
Side effect of BPE is to move shockie out from its usual mount giving revised open and closed stops for the suspension.
In my case I am hoping to get slightly more axle drop using some of the unused shockie travel under full compresion.
Marcus ohms has photos of Bar pins and some extenions at
http://go.jeep-xj.info/Exterior.htm