Dopper 12L 232Bar DIR Style black concave. The diving bottles have a concave bottom. Concave means curved inwards and not round. 
 
The concave bottom has several advantages.
 
1. Due to the concave bottom, the diving bottle stands without an additional stand. A stand is not required.
 
2. The knkaven scuba tanks have the advantage that they are about 500g heavier at the end of the bottle than scuba tanks with a round bottom. This allows divers to position the diving tanks a little higher in the clamps, making it easier to access the valves. The optimal trim is retained.
 
Details:
Double 12L, 232Bar DIR Style black concave,
OMS clamp set with reinforced bridge,
bottle color black,
Valve combination from Scubatec with shut-off bridge,
Bottle length 685 mm
Bottle diameter 171 mm