Yeah NY is that screwed up.
I don't remember the exact details but you could have I want to say three 'oooh bad' items.
IE: flash hider, bipod, forward grip, adjustable stock etc.
Basically anything to make your weapon more user friendly, because it's a scary black gun you can only have three. Now it may be two of them too, I dont exactly remember. Also they are limited to 10 round mags.