Hey guys quick question, I’ve been having some major leaking issues with my used-to-be favorite Avent bottles and I’ve tried everything to fix it but nothing works. So I’ve decided to go back to these Tommee Tippee bottles we got at our shower. I didn’t use them much when we got them because there were just too many parts and I got tired of cleaning them, to be honest. But I was wondering if I can use the bottles without all the parts pictures below? The piece I’m holding is three separate parts, I don’t really know the purpose of them or if they’re *really* necessary. Thanks in advance!

Update: I tried it out with just the white piece and it was leaking SO BAD. I’m not sure what I did wrong lol..