These are 1/2" Grade 8 zinc-plated ubolts are 8.5" long and a huge upgrade over the stock 12mm ubolts and we include grade 8 nylock nuts to provide many years of service. These bolts work great with OME and Alcan or Deaver leaf packs (these are too long as just replacement ubolts). These are good for upto 2" blocks also. The tight through the factory spring plate is tight and may need a little wiggle, but they will go.