I have the oyster 3 carrycot and stroller seat already, can I use these on the oyster max frame if I get one? Also, which adapters would I need?
I'm afraid I'll disappoint you, but no, you cannot use the Babystyle Oyster 3's seat nor the carrycot on the Oyster Max chassis. It's larger so the center of gravity as well as the space for it would be so changed it might be actually really bad to push to actually dangerous (tipping etc.).
You can only pair it with an Oyster 2's seat that was made the same )but even that, only on the main position.
The required adaptors are normally included with the stroller itself or with the second seat attachment. You can ask the seller, if you're talking about a new one, whether it's included or sold separately in their shop - and ask for the separate pair in your order if they sell it optionally.