It came from the factory with 1/2 bolts, but I ordered 5/8 eye leafs and shackles, all come with new bushings/bolts. Instead of 1650 rating per spring it's moved to 1700 per spring. Both my RC's have 5/8 so that's what I went with and besides, it was actually a lot cheaper to go beefier. This would be the grand time to install a different rear end, means the U-bolts will be loosened.