APEKS US4 1ST STAGE ONLY
PRODUCT DETAILS
Small, simple, and seriously useful for auxiliary gas setups
The Apeks US4 First Stage is the minimalist 1st stage built for divers who value tidy, low-profile gas delivery on inflation and suit-feed cylinders. Unsealed and uncomplex, it keeps the footprint tight while giving you the routing options you actually need on travel bottles, pony cylinders, or dedicated suit inflation gas.
Compact design, practical ports
Its small brass body tucks neatly onto sidemounted inflation cylinders or stage bottles without snag points or sharp edges. With 4 × 3/8 medium-pressure ports and 1 × high-pressure port, it lets you route multiple feeds cleanly — perfect for suit inflation, wing fills, or SMB practice bottles without clutter.
Pressure you can tune
While it’s unsealed by design, it still carries Apeks system sensibility with an adjustable intermediate pressure — letting you dial your setup to the sweet spot your 2nd stage or inflator likes best. No presets. No surprises. Just controlled delivery you configure once and trust every dive.
A superstar on small inflation cylinders
Commonly selected for air or enriched gas inflation bottles, it happily supports suit feeds in temperate profiles and is often seen on drysuit inflation rigs clipped to hardware from Halcyon or compact sidemount staging used across UK training sites like Capernwray.
Know where it fits
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Primary backmount reg? Choose a sealed 1st stage instead
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Dedicated inflation or suit cylinder? This is your tidy solution
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Cold water? Best when used above 10°C or on protected inflation cylinders
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OOA safety chain? Works upstream, but pair with sealed 1st stages for true cold-layer resilience
US4 Stand-Alone 1st Stage — key benefits
✔ Ultra-compact, unsealed brass body
✔ 4 × 3/8 MP ports for clean multi-feed routing
✔ 1 × HP port for tidy gauge or transmitter alignment
✔ Fully adjustable intermediate pressure
✔ Ideal for suit, wing, or SMB inflation cylinders
✔ Minimal size, maximum staging practicality
✔ Designed in the United Kingdom for divers who rig sensibly
Route cleaner. Tune smarter. Keep your inflation gas low-drag and high-control. 🤿