Which Magpul Sling will work with my stock Smith & Wesson M&P 15 Sport II? It came with D-rings installed and I don't care about quick disconnects, though I would like to be able to convert it from single-point to dual-point as necessary. I'm looking at MS1, MS2, MS3, or MS4.

If I bought an MS4, what would I need to use it with my AR?

I'd like to know ASAP so I can place my order today. Thanks in advance!