THESE BOLT-ON D-RINGS are made of exceptionally heavy duty solid steel, 1/2" diameter thick. They are strong and durable, and can handle a load up to 4000 pounds. That means that these 4 rings can bear up to 16,000 pounds together! See the description for a clear guide on how to figure out your tie-down limits when loading cargo on trucks and trailers, especially if you're up for DOT inspection... | SEE THE 7th PICTURE for a clear visual image of all the dimensions to make sure that this is the tie down you need. Please realize that these rings do come with 3" x 1 3/4" bolt-on mounting brackets but NOT installation bolts. Use 3/8" carriage bolts to secure. | BOLTED D-RINGS are the most handy and flexible tie-downs available. Generally used as tie-down anchors on trucks, pickups, campers, vans, docks, boats, flatbeds, and trailers, they’re also handy as wall hooks in organized garages, warehouses, and workshops. These D-Rings are Zinc plated for superior corrosion- and rust- resistance- 'Color may vary' | 3 1/2" x 3 1/2" inner clearance. Once these D-rings are mounted, you can USE THEM AS TIE-DOWN ANCHORS for motorcycle straps, bungee cords, tarp straps, small chains, ratchet and cam straps, ropes, and other tie-downs. Ideal for securing kayaks, ATVs and other powersport equipment, bikes, refrigerators and similar appliances, delivery and moving boxes, camping gear, etc. | This tie-down anchor also comes in a 4-pack or as a smaller 3/8" or 1/4" diameter.