Building a backmount twinset

A configured double set is just five matched parts — but every one has to fit the others. Here’s the checklist, and when to buy a complete set instead of building from components.

6 min readTwinset configuration

Key takeaways

A double set = two matched cylinders, a manifold, two tank bands and bolts, plus boots.
The manifold must match cylinder diameter (171/203 mm) and pressure (232/300 bar).
Left cylinder takes a left-hand valve; right takes a right-hand valve.
Complete twin sets (€645–856) come assembled and matched — the simplest route.

The five parts

Building a backmount double from components is straightforward once you know the parts have to match each other. Get the diameters and pressure ratings consistent and the rest follows.

Two cylinders

Matched steel cylinders as back gas — same diameter and pressure rating. Steel for consistent negative buoyancy and capacity.

A manifold

Sized to the cylinder diameter and pressure, with the central isolation valve.

Two tank bands

Stainless steel bands clamp the cylinders at the correct spacing for your backplate.

Bolts, boots & protectors

Twin tank bolts set the spacing; boots and EPDM protectors finish and cushion the set.

Match before you buy Confirm three things agree across every part: cylinder diameter (171 or 203 mm), working pressure (232 or 300 bar), and valve thread format. An incorrectly sized manifold won’t seat or seal, and mixed pressure ratings are unsafe.

Left and right matter

The left cylinder takes a left-hand valve, the right a right-hand valve. This sets which way each knob turns, which is what makes the standardised valve shutdown drill work the same way every time. Get this wrong and your trained muscle memory works against you.

Build or buy complete?

If you already own matched cylinders, building from components lets you reuse them and choose each part. If you’re starting fresh, a complete twin set — cylinders, manifold and bands assembled to spec — removes every compatibility question and arrives ready to dive. It’s the simplest route and usually the safest for a first double set.

Training first Backmount doubles and manifold configurations are technical equipment used with technical training. The valve drills, gas management and failure procedures are taught before you dive a twinset — buy the hardware alongside the course, not instead of it.