The 100 pound frag bomb cluster AN-M1A2 consists of six 20 pound frag bombs AN-M41A1 assembled in cluster adapter AN-M1A3. The cluster adapter AN-M1A3 is a “quick-opening frame,” a mechanical type of adapter which holds the bombs in two banks of three bombs each and releases them upon withdrawal of the arming wires. The bomb cluster is issued with individual bombs assembled but unfuzed; fuzing is performed before the cluster is installed in the aircraft. Cluster adapter AN-M1A3 has four sheet-metal bomb supports spaced at intervals on two tubes. Three flat steel suspension lugs and two side plates are attached to the upper tube. Two spring strips are fitted to the bottom tube. Fuze-vane lock springs fit into a ferrule in front of the spring strips. Three lock springs pass through the front support and three through the third support. The fuze-vane lock springs prevent rotation of the fuze arming vanes while the bombs are in the cluster. Two metal straps hold the bombs in place against the adapter; their free ends are locked in place by a toggle strap clamp secured by the arming wire.
The difference between frag bomb clusters AN-M1A1 and AN-M1A2 lies in the cluster adapters. The AN-M1A1 uses the cluster adapters M1A2 or M1A1 (instead of the M1A3) which has narrow U-type suspension lugs; with these lugs, the complete weight of the cluster is only 125 pounds. US Cluster, 100 lb Frag, AN-M1A1, AN-M1A2, M1 (bulletpicker.com)