I am a known Diabetic for last 20 years under insulin . The doctors frequently precriping differant type of insulin . I used to buy the permanent pen + disposable insulin cartrdidges everytime for that brand , like Huminsulin 30/70 , Mixtard 30/70 and now Lantus , solo star . My questuon is whether these pen and cartridges are standardised ? Shall we put any cartridge on any pen ?