I'm not sure, but I don't think they make the M-5 any more. Here's another nice quality light that is very bright......I purchased mine through Longhorn Tactical.
Pretty sure the Olights come with a couple different adaptors for 1913/Picatinny/Glock style rails. I have an Olight PL-Mini Valkyrie on my Compact M2.0 that did. Olight makes excellent quality lights of all kinds and at very competitive prices.