Yes, its needed in order to engage the clutch. The generic carts are fatter AND shorter than the novo carts.Do you know if it will work without a ring spacer? I can get the adapter from insulin cartridges, whcih i suppose will fit on the generic ones. But dont have ring spacers.
Also big note for anyone that wants to use the Novo pen. They are great quality but because of the size difference they also OVERDOSE by 8%. You can account for it though.

