4-pack - Recessed Pan D-ring Trailer Tie Downs (6,000 Lb. Capacity) and Heavy Backer Plates, Including Mounting Hardware (Complete Set: 16 Carriage Bolts, Washers and Nylon Lock Nuts) 4 complete sets of D-rings, backing plates and 2 1/2" hardware kits. Both components are zinc coated to inhibit rust and corrosion. The d-rings have square holes punched for receiving carriage bolts, providing a smooth and relatively trip free surface. When in use the ring portion raises for application and lies down when not in use, thus creating a flush surface. It is plenty strong and is able to receive multiple tie-down straps simultaneously. Each D-ring has a 6,000 lb straight pull capacity. 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 tie-down should be subjected to during normal use. To assist in making the proper tie-down choice the Federal D.O.T. requires the W.L.L. to be 1/3 of the Rated Capacity. SPECIFICATIONS of d-ring: 1) The base measures 5" x 4-1/2". 2) Hole pattern is 3" x 3-1/2" on centers. Recessed dimension is 3" diameter with a flat edge. 3) The 7/16" diameter ring measures 1-3/4 center. 4) The ring pivots on a 5/16" threaded stud. 5) The pan has a 1/4" drainage hole. HARDWARE: This listing comes with four (4) hardware kits, enough to complete the installation. Each kit comes with 4 - 3/8" x 2-1/2" long carriage bolts, 4 - fender washers, and 4 - 3/8" nylon locking nuts. BACKING PLATE is used for support under the floor when installing the tiedown attachments, and prevents the bolts from pulling through. SPECIFICATIONS: 1) The backing plate measures 6-1/2" x 6-1/2". 2) Thickness is 11 gauge (a little thinner than 1/8). 3/8" holes. 3) 3-1/2" diameter cutout. 4) Steel backing plate is zinc coated to inhibit corrosion. INSTALLATION - these D-rings require routing, or cutting a hole in the floor. We recommend creating/cutting a template and then transferring to the desired location. If you use a 3" hole saw, the d-ring will fit without any further work. Better fit - use a 2-1/2 hole saw then jigsaw the flat edge and then bevel the edge with a wood hasp to create a snug fit.