High Quality Content by WIKIPEDIA articles! The Massive Ordnance Penetrator (MOP) GBU-57A/B is a U.S. Air Force massive, precision-guided, 30,000-pound (13,608 kg) "bunker buster" bomb. This is substantially larger than the deepest penetrating bunker busters previously available, the 5,000-pound (2,268 kg) GBU-28 and GBU-37.