These are aerial dispensed, antitank shaped charge, bombletts. After nose impact with either a soft or hard targets the bomblett would detonate. The MK118 had problems with this when encountering soft soil like sand they would not function. The BLU77 was designed to fix this problem as well as add more fragmentation for anti personnel. Both MK118 and BLU77 are dispensed by MK7 and mk20 dispensers a lightning bolt painted on the side of the MK7 indicates BLU77 submunitions are the payload.