Hardware Kits: This listing comes with 4 hardware kits, enough to complete the installation. Each kit comes with 4 3/8" x 21/2" long carriage bolts, 4 fender washers, and 4 3/8" nylon locking nuts. The 2.5" bolts are long enough to go through 2" thick planks which is typical on an open trailer. IMPORTANT Most enclosed trailers have 3/4" thick floors. The 2.5" long bolts will work on 3/4" floors but are longer than what is needed. Therefore if you prefer 11/2" bolts please message us and we'll be happy to provide the shorter bolts. APPLIES to seller fulfilled orders only. This tie down attachment has a 6,000 lb. capacity* vertical pull weight rating. To install this attachment requires routing, or cutting a hole in the floor. This recessed dring has square holes punched for receiving carriage bolts, providing a smooth and relatively "trip free" surface. The steel attachment is zinc coated to inhibit corrosion. When in use the ring portion raises for application and lies down when not in use, thus creating a flush surface. This tie down attachment is plenty strong and is able to receive multiple tiedown straps simultaneously. To obtain maximum strength it is recommended to install these drings with bolts, lock nuts, and fender washers. For installation purposes it is easiest to cut a template and then transfer to the desired location. * RATED CAPACITY: Also known as "assembly capacity" or "break strength" is the minimum load a complete assembly can withstand before failure in a laboratory pull test when the product is new. ***WORKING LOAD LIMIT: The maximum load weight a tiedown should be subjected to during normal use. To assist in making the proper tiedown choice the Federal D.O.T. requires the W.L.L. to be 1/3 of the Rated Capacity.