First of all i have no idea what the difference is.
Anywho, my question is, on my m4 i have a
http://airsoft-club.com/shop/externa...ard-for-m4-aeg
i understand how its mounted. but as for things like...
http://www.airsoftgi.com/product_inf...oducts_id=6381
would i need to buy an extra piece or something? o.o