After going through the measuring and observing process, we learned our XJ had an early-model NP 242, and that the U-joint dimension was 3-7/32 inches. We also measured the stock driveshaft from the edge of the seal at the transfer case to the center of the U-joint at the axle end. We provided all this information to Tom, and he assembled our SYE kit and built the driveshaft. The driveshaft is Tom's "XB" configuration, which features a long slip spline and a heavy-duty rubber boot that totally seals contaminants out of the driveshaft's slip yoke. The Tom Wood "XB" configuration is what Tom considers "the longest lasting and the best value."