Yes. The MAG540 is compatible with any standard push-button QD sling swivel socket, regardless of manufacturer. The QD socket standard is consistent across the industry, so this swivel will function with QD cups from any reputable manufacturer — on end plates, buttstock cups, handguard mounts, and any other standard QD attachment point.

Manganese phosphate is a conversion coating applied to steel that creates a porous, matte black surface layer with good corrosion resistance and excellent oil retention. It is one of the traditional mil-spec finishes for steel firearms components, prized for durability and the ability to hold lubricant in the surface pores. On a sling swivel that will see repeated contact with sockets, webbing, and outdoor exposure, manganese phosphate provides reliable long-term protection without significant dimensional buildup on the part.

A two-point sling requires two QD attachment points — one at the rear (typically a buttstock or end plate cup) and one at the front (typically a handguard mount or sling cup). If your sling does not already have QD swivels sewn in at both ends, you will need two of the MAG540. Some slings include swivels; check your specific sling’s included hardware before ordering.

The Magpul MS1 MS4 Adapter is a separate accessory that allows the MS1 two-point sling to convert to a one-point configuration. It works in combination with the MAG540 swivel. If you only want a fixed two-point setup, you do not need the adapter — the MAG540 on its own with the MS1 sling gives you a standard two-point. The adapter is only necessary if you want the convertible one-point / two-point functionality similar to the MS4 sling.