5 Compact Aluminium Cylinders for Configuration Planning
Compact cylinders have specialist roles that depend on the complete configuration. These five models differ in gas capacity, length and end-of-dive buoyancy. They are presented for trained divers planning an appropriate system, without assigning bailout duration or treating any size as universally adequate.
Updated · Manufacturer specifications and published review evidence
How we chose and ordered these picks
Higher-capacity compact options lead, then progressively smaller cylinders. This is a dimensions-and-capacity comparison, not a bailout sufficiency ranking.
List position is an editorial recommendation, not a review score. The selection uses the documented features and limitations below. We have not personally tested this equipment. Verified publisher scores, where available, are shown separately and link to their evidence. Our catalogue is still being researched; inclusion does not mean a product has a completed scored review.
The shortlist at a glance
Choose a model to jump to its details. Compare the exact configuration before ordering.
Exact-model photo not yet verified. See the manufacturer specifications for dimensions.
S45 is a short, relatively broad aluminium cylinder with 6.4 litres of water capacity and 45 cu ft of air capacity. Its 450 mm length is useful to compare against taller cylinders, while the 175 mm diameter and 9.2 kg weight prevent it being mistaken for a narrow stage bottle.
Water / air capacity
6.4 L / 45 cu ft
Service pressure
3000 psi / 207 bar
Diameter × cylinder length
175 × 450 mm
Cylinder weight
9.2 kg
Buoyancy: full / 500 psi / empty
-2.8 / -0.3 / 0.5 lb
What to check
Catalina lists buoyancy moving from -2.8 lb full to +0.5 lb empty. The official page currently supplies a placeholder rather than an exact product photo; the previously assigned logo has been removed. Check local supply and valve options directly.
No verified independent overall score yet. Compare the specifications and limitations above.
Exact-model photo not yet verified. See the manufacturer specifications for dimensions.
The S40 is Catalina’s narrower 5.8-litre aluminium scuba cylinder, with a listed air capacity of 40 cubic feet at 207 bar. At 133.4 mm diameter and 645 mm cylinder length, it has very different proportions from an S80. Its size can be useful for a separately rigged cylinder where the required gas volume has been established.
Material
6061 aluminium
Water capacity
5.8 L
Air capacity
40 cu ft / 1132 L
Service pressure
3000 psi / 207 bar
Dimensions
133.4 mm diameter × 645 mm length
Cylinder weight
7.3 kg
Listed buoyancy
-1.5 lb full; +0.7 lb at 500 psi; +1.4 lb empty
What to check
Catalina lists a 7.3 kg cylinder weight and buoyancy of -1.5 lb full, rising to +0.7 lb at 500 psi. Valve, regulator and rigging affect the assembled result. A smaller cylinder is not automatically adequate as an emergency supply; capacity must come from the dive plan. Confirm markings and acceptance with the filling provider.
No verified independent overall score yet. Compare the specifications and limitations above.
S30 combines 30 cu ft air capacity with a 4.3-litre internal volume. At 133.4 mm across and 505 mm long, it sits between Catalina’s narrow S19 and longer S40. The listed 6.2 kg cylinder weight makes transport and mounting more substantial than its compact capacity suggests.
Water / air capacity
4.3 L / 30 cu ft
Service pressure
3000 psi / 207 bar
Diameter × cylinder length
133.4 × 505 mm
Cylinder weight
6.2 kg
Buoyancy: full / 500 psi / empty
-2.4 / -0.7 / -0.2 lb
What to check
Catalina lists -2.4 lb buoyancy full and -0.2 lb empty. Treat these as cylinder specifications, not a weighting prescription for an assembled system. Verify the actual valve, markings and inspection history before choosing a used example.
No verified independent overall score yet. Compare the specifications and limitations above.
S19 holds 19 cu ft of air in a 2.7-litre aluminium cylinder. Its 111.3 mm diameter matches the smaller S13, but the 450 mm length gives it a noticeably taller profile. Catalina lists 3.5 kg before adding the rest of a breathing assembly.
Water / air capacity
2.7 L / 19 cu ft
Service pressure
3000 psi / 207 bar
Diameter × cylinder length
111.3 × 450 mm
Cylinder weight
3.5 kg
Buoyancy: full / 500 psi / empty
-1.5 / -0.4 / -0.2 lb
What to check
The manufacturer’s buoyancy table remains slightly negative when empty. Check the complete rig rather than assuming the cylinder figure includes your valve, regulator and clips. Its capacity must follow a gas plan, not a generic “pony bottle” recommendation.
No verified independent overall score yet. Compare the specifications and limitations above.
S13 is Catalina’s short, narrow aluminium cylinder: 1.9 litres of water capacity in a 325 mm body. The 13 cu ft air capacity and 2.6 kg cylinder weight make it a compact option when a separately planned small gas supply is required.
Water / air capacity
1.9 L / 13 cu ft
Service pressure
3000 psi / 207 bar
Diameter × cylinder length
111.3 × 325 mm
Cylinder weight
2.6 kg
Buoyancy: full / 500 psi / empty
-1.8 / -1 / -0.9 lb
What to check
Catalina lists the bare cylinder as negatively buoyant even when empty. That does not establish the buoyancy of a regulator-equipped assembly. A compact bottle is not automatically an adequate bailout supply; capacity, valve and local filling acceptance must suit the intended configuration.
No verified independent overall score yet. Compare the specifications and limitations above.
Product research checked 2026-10-03. Specifications can change; confirm the exact model and package.
Before you buy
Calculate requirements for the intended role with appropriate training.
Check mounting, valve protection and connection compatibility.
Distinguish water volume from rated free-gas capacity.
Take two or three suitable models from this list into a comparison, then remove any that fail your fit or compatibility checks. A lower position here can still be the better purchase for your setup. Check the product page for source dates and unresolved details before placing an order.
How long will one of these cylinders last?
There is no single duration. Depth, breathing demand, starting pressure and reserve requirements change usable time; this guide does not substitute a fixed estimate for gas planning.
