Ancra Aluminum Track Fitting 4,000 lb. Capacity Tiedowns w/Steel Keeper 6-Pack This listing is for six (6) single stud fittings with a RATED CAPACITY* of 4,000 lbs. The W.L.L.** (working load limit) is a 2,166 lb. capacity. This fitting fits all aluminum track that is similar to the track shown in the secondary image above. We refer to the track as aluminum load track. It is also commonly referred to as airplane track, seat or simply S track. *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. **W.L.L. 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. The fitting is SPRING LOADED to permit simple attach and detach operation. To detach, simply pull up on the spring loaded mechanism and then slide forward or back and the fitting releases. To attach, rest the fitting in the load track, then push down on the base and push forward. Single stud refers to the number of "fingers" that it captures when attached to the aluminum track. The base measures 1-3/8" long x 3/4" wide with a 3/16" diameter stainless steel ring that measures 1-3/8" on center. The fittings' stainless steel ring will not rust. The steel stud/center post and base (keeper) are zinc plated to inhibit corrosion.