The Human Engineering Lab's HEL-E4A was the most commonly used suppressor used in the Vietnam War. It was the result of a series of suppressor designs from the Aberdeen Proving Grounds HEL which were developed to balance suppression and back pressure, so that they could operate reliably on a standard M16 rifle. A total of 960 were sent to Vietnam in late 1968 and early 1969 (in addition to 120 earlier HEL-M4 pattern ones). Today they are extremely rare, as very few came back from the war.

The example I am using here is a new reproduction made by International Milspec Co (Intl Mil Co).