ASF (Ambidextrous Selector, Forward Controls) centers are available in all four configurations: 50 degrees, 90 degrees, conventional M16 (0-90-180), and short throw M16 (0-50-180, SAFE to SEMI is 50 degrees short throw, AUTO/BURST is unchanged, 180 degrees from SAFE).
ASF centers are compatible only with ASF levers. Each ASF center is shipped with 4 additional roll pins, a KNS stainless steel, black nitrided detent, and a selector detent spring.