not sure if this helps?
you can use the parts with other bottles- i learned that from 2 posters from another board:
Born Free bottles with the wide mouth Dr. Brown’s nipples and vents: They work great and there are no leaks.
Dr. Brown’s nipple and vent system fits the colored evenflo bottles – $3 for 3. They are BPS free and MUCH cheaper than the Born Free. In the plastic bottles, the vents work fine without being trimmed. They don’t go straight down, they veer off center slightly – but with no problems at all.