It’s stock afaik. Shoots like a dream, it’s not probably shooting around 16-20 rps with the battery peq (11.1 lipo) Has a tri rail, I wired it externally cause it’s so much easier than fitting a tiny battery in the shroud. Comes with 14 mags, I believe 4-5 are hi cap and the rest mid caps. Some metal some plastic, all feed well. Ebb still functions perfectly, most people selling these say they disabled the ebb because they didn’t like it (but u buy this model FOR that...) which means it’s heavily used and/or they did a little too much “HK slapping” Great deal, will raise price back up if not sold this weekend (was at 350)