Not a SOG used item but one more commonaly associated with Navy SEAL Teams in Vietnam, often taped to a knife scabbard.

The Mk 13, Mod 0 signal flare is attract the attention of SAR aircraft 11-15-7 for signal kit. intended to and to give them drift direction. To avoid being burned by sparks, the ignited Mk 13, Mod 0 signal must be held at arms length and no more than shoulder high. If the Mk 13, Mod 0 signal is being used at sea, hold it over the side of the life raft to prevent damage to the life raft from hot residue. The Mk 13, Mod 0 signal may be put out by dousing in water or snuffing in sand. The Mk 13, Mod 0 consists of a metal cylinder closed at each end. There is a tear friction tape igniter on a clip at each end. One end contains a red flare for nighttime use; the opposite end houses an orange smoke signal for daytime use. Each end of the signal burns approximately 20 seconds. The nighttime end of the flare has protrusions that you can feel in the dark.