steel cartridge from abs . the steel cartridge contains inert gas (non-flammable, non-toxic, part of the breathing air) and fills the abs twinbags in 2-3 seconds regardless of temperature or external pressure load. the cartridge weighs 512 g and the unit is easy to change and refill.it is compatible with the abs backpacks a.light, s.light, s.cape and the vario base unit.