half inch. But XJ shackles are too short for the MJ leafpacks. One guy actually had an XJ shackle flip up on him.
Explorer leafpacks can also be used. In fact, if that truck was mine, I'd go get a set of Explorer leafpacks, cut the eyes off, and put the entire thing under the current MJ main leaf. The truck will sit a bit lower, and you'll get the added benefit of the extra leaf helping to fight springwrap. :thumbsup: Just be aware that the Explorer leafpacks use a slightly larger centering hole and you'll need to bore out the MJ main leaf a tiny amount to use the bigger bolt.