The RCBS 9550 or the RCBS Universal Primer Arm 2 is specifically crafted for speedy and precise primer seating. It includes primer plugs and sleeves suitable for both large and small rifle and pistol primers. This feature enables quick and easy size changes, taking less than a minute. Compatibility extends to Rock Chucker II, JR, Reloader Special and a majority of C presses. However, note that this item is incompatible with the Rock Chucker Supreme.