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Wings for doubles backmount configurations in the 20–30 litre range. These bladders are sized for twin-cylinder setups where the combined negative buoyancy of two steel cylinders requires substantially more lift than a singles wing provides. Two series dominate this range: the Donut XL (20l) and the Donut XTECH (20l and 22l), each available in Cordura and Kevlar constructions.
Wing Geometry for Doubles Diving
Doubles wings operate under higher load than singles wings — two steel 12l cylinders at depth carry significant negative buoyancy, and the wing must provide enough lift to control ascent rate and achieve neutral buoyancy across the diver’s target depth range. The 20–22l capacity range is the technical standard for twin-cylinder backmount diving and provides adequate lift margin without creating an over-buoyant profile at depth when the bladder is partially inflated.
The Donut XL 20l series uses a traditional donut cross-section that wraps uniformly around the doubles manifold. Available in Cordura (240092/3/G/H — multiple colour variants), KEVLAR (240095), KEVLAR+ (updated Kevlar construction with reinforced attachment points), and Mix (Cordura body with Kevlar reinforcement at contact zones) and special editions (No-Cut and other limited fabrics). The Donut XTECH 20l series uses a modified X-shaped internal baffling that constrains lift to the outer margins of the bladder, keeping the diver’s back profile flatter and improving trim. Available in Cordura (240050/2/C) and KEVLAR (240053). The Donut XTECH 22l variants add 2 litres of capacity for divers using larger diameter or longer cylinder configurations where additional lift is needed (Cordura 240055/6/B, KEVLAR 240057). The Bladder for Comfort/Basic Tech (230211) is the replacement bladder for the COMFORT TECH and BASIC TECH complete BCD systems, with a geometry matched to those specific backplates.
What to Look For
- 20l vs. 22l — choose 20l for standard steel AL80/S80 doubles and most steel 10–12l twin configurations. Choose 22l if diving large-volume steel doubles (2×15l) or in cold water with a thick drysuit undersuit where maximum surface lift is needed for exits.
- XL vs. XTECH geometry — the XTECH baffling improves horizontal trim by keeping the bladder profile lower on the back. Divers who are already comfortable with their trim on an XL and do not need the extra discipline of baffled lift distribution will not notice a meaningful difference. The XTECH is recommended when trim precision is a priority.
- Fabric selection — Cordura for general use; Kevlar for cave and wreck penetration or any environment with sustained fabric contact with abrasive surfaces; Mix for divers who want Kevlar protection at high-wear zones without the full weight of an all-Kevlar wing.
- System compatibility — verify that the bladder’s mounting geometry matches your backplate. The Bladder for Comfort/Basic Tech is specific to those BCD systems and is not a universal drop-in replacement.
FAQ
What does KEVLAR+ mean compared to standard KEVLAR?
The KEVLAR+ designation (LZ 14 bladder in Kevlar+, Donut XL 20l KEVLAR+) indicates an updated Kevlar construction with reinforced stitching and additional lamination at the highest-stress points — typically the OPR valve mount, inflator attachment, and backplate loop. The base fabric is the same para-aramid Kevlar; the + variant addresses long-term durability at stress concentration points that the standard Kevlar construction showed wear at after extended use.
Can I use a doubles bladder for single-tank diving?
Technically yes, but it is not recommended. A 20l doubles wing on a single cylinder creates an over-buoyant system at depth — the bladder at even partial inflation provides more lift than required, making buoyancy control imprecise. Use a 12–14l singles wing for single-cylinder diving and a 20–22l doubles wing for twin cylinders.