To assemble a set of double cylinders, you are going to need a variety of items. �€� To begin, you are going to need a set of tank bands. For manifolds with 8 1/2 center spacing, Dive Rite's Heavy Duty GM1037 bands fit 8.0-inch/20-cm diameter, high-volume steel cylinders that are most popular among technical divers, or Dive Rite's special Heavy Duty GM1033HD bands for cylinders with diameters up to 7.5 inches/19 cm. �€� To bolt your cylinders together, choose the Bolt Kit that coordinates with your bands. �€� To mount your doubles to a Dive Rite TransPac harness, you'll need a set of GM2084 stabilizing plates.