"The GBU-57 series MOP (Massive Ordnance Penetrator) is a 30,000-pound (13,600 kg)-class precision-guided "bunker buster" bomb developed for the United States Air Force (USAF)...It is much larger than earlier USAF weapons designed to destroy heavily fortified, deep underground bunkers such as the 5,000-pound (2,300 kg) GBU-28 and GBU-37"