Model Number: carbon dioxide cartridge Brand Name: DN Key Specifications/Special Features: These CO2 cartridges are widely used with fire extinguishers, there are two types, one is internal cartridge, and one is external cartridge Size250G 280G 300G 350G Item no. DN31-01 DN31-02 DN31-03 DN31-04 OD 51mm 51mm 51mm 51mm Volume(ML) 375 420 450 525 CO2 filled weight (G) 250 280 300 350 Cylinder length(mm) 280 310 330 390 Test pressure (bar) 250 250 250 250 Min WT (mm) 3 3 3 3 Material 20# 20# 20# 20#