A marine mammal back-mount transmitter is glued to the back of a seal's head or neck using various epoxy adhesives. The antenna is vertical. This attachment method works well for tracking haul-out sights and breeding grounds. The transmitter will fall off when the seal molts. Field range is good when the seal is beached. However, when the seal is submerged, the water attenuates the VHF signal. Many models include the enhanced range option (denoted by "B" suffix).

Series	Weight (grams)	Life (days)	Description
MM100	7-36	58-540	Cylindrical shape, flat bottom, single battery. Enhanced range option available.
MM200	52-89	370-1080	Cylindrical shape, flat bottom, (2) batteries. Enahced range option all models.

A marine mammal head-mount transmitter is glued to the top of a seal's head using various epoxy adhesives. The antenna is vertical at a 45º angle. This attachment method works well when the seal is submerged and only their head is out of the water. This method is used to track seals at sea, usually to determine their foraging patterns. The transmitter will fall off when the seal molts. Field range is good when the seal is beached or its head is protruding out of the water.

Series	Weight (grams)	Life (days)	Description
MM300	57-92	370-1080	Cylindrical shape, (2) batteries, antenna at 45º angle. Enhaced range option all models.