I ordered one up from a CA rifle parts supplier. Basically it makes the Magazine non detachable without a "tool". I am popping this on the A2 and taking back to mom's place for the 4th. We have an agreement now that we can shoot as long as cows aren't grazing around the house. Wording of NYS law; "Assault weapon" is defined as: A semiautomatic file that has an ability to accept a detachable magazine and has at least two of the following characteristics: Now NY doesn't have a legal definition of "detachable" but I believe the BATF does.