The BLU-109/B has a steel casing about 1 inch (25.4 mm) thick, filled with 530 lb (240 kg) of Tritonal. It has a delayed-action tail-fuze. The BLU-109 entered service in 1985. It is also used as the warhead of some marks of the GBU-15 electro-optically guided bomb, the GBU-27 Paveway IIIlaser-guided bomb, and the AGM-130 rocket-boosted weapon. This weapon can penetrate 4-6 feet of reinforced concrete, which is greater than the 3 foot capability of the Small Diameter Bomb. The BLU-109 is not likely to be retired anytime soon, due to the much larger blast capable from its warhead.