What is the purpose of the fins inside this faucet cartridge? And does it matter if the replacement has slightly different dimensions?

The original cartridge is on the left and, as you can see, it doesn’t have the white fins inside of it. Curious what those fins do.

I replaced it with the one on the right after it started leaking even when fully shut. The replacement is a bit larger, but seems to fit fine. There is no leak and the handle went on fine too. Is there any problem that this could cause that I wouldn’t immediately notice?

Thanks!