The Scott Sigma 2 Type 2 is an open circuit, self-contained, compressed air breathing apparatus. It consists of a back plate, carrying harness and pneumatic system, containing a reducer with integrated cylinder connector, pressure gauge, whistle and demand valve. The Sigma 2 Type 2 can be confi gured in a number of different ways with various sized single cylinders and the choice of Vision 3, Panaseal, Panavisor or Promask PP facemask.