A buoyancy compensator device (also referred to as a BC or BCD) fits like a backpack and holds the tank securely, both above and below the water. The main purpose of the BC is to assist divers with controlling their position in the water column; adding air from the tank to the BC’s internal bladder allows the diver to rise, while venting air allows the diver to sink. A properly inflated BC will help keep the diver at the desired depth during the dive. A diver has to be properly weighted to allow for his body composition and gear, and where divers always used weight belts today most BCs contain integrated weight pockets, where a diver inserts weigh packets for the proper adjustments.
The links for the buoyancy compensators below will take you to the corresponding page at California Diving News’ sister publication Dive Training Magazine. There you will find a full description of the product.
TUSA BC0201 Conquest II
Sherwood Scuba Axis
Mares Prestige MRS Plus