The clamp on fabricated mounts cost less then the cast versions, but do not have quite as much clamping force. The axle clamps are made with 1/4" wall mild steel tubing and are held together with two 1/2" grade 5 bolts. These mounts should be tack welded or bolted to the axle tube. Even with a tack weld, they will not warp the tubes like the weld on style mounts.