These tie-down rings are made of exceptionally strong, 1/4" diameter solid steel. They are strong and durable, have an assembly breaking strength of 1,200 lbs and a working load limit of 400 lbs per pack. This D-ring anchor adds a sturdy anchor point for ropes, cables, straps, or chain, and can be easily attached to a metal surface or wood floor with just two bolts and basic hardware. Bolts are NOT included. Bolt-on D-rings are convenient and flexible fasteners available. Typically used as anchor points on trucks, pickup trucks, RVs, vans, docks, boats, flatbeds, and trailers, they are also handy as wall hooks in organized garages, warehouses, and workshops. Each size: D-ring measures approximately 40mm x 48mm / 1-1/2" x 1-7/8" with 6mm / 1/4" diameter and the mounting bracket measures approximately 53mm x 20mm / 2" x 3/4" with 6mm / 1/4” hole. Each package includes 12 packs of D-ring tie-down anchors. Please note that these rings come with bolt-on mounting brackets but NOT