With Turbine helicopters, the eternal problem is getting enough fuel on board for descent flight times.  And there are a few way to do this, increase the size of the internal tanks or add more tanks.  We have decided to specialise in external metal tanks, and have chosen to partner with MSR.  Mountain Scientific Research produce a really good fuel bottles in 3 sizes, they are made from a single piece of impact-extruded aluminium to prevent leaks and cracks.  MSR have been designed the bottles with a thicker aluminium at neck and thread is turned directly into that. most other manufacturers use a pressed fitment in the neck of the bottle.  With bolstered shoulders & base to resist bulging when pressurised.  Our tops ensure an air-tight seal, which allows fuel to be stored longer by preventing air from entering and degrading fuel.