some people have issues with bumps forming and claim that leaving the lid off when freezing helps alleviate it. here's an option for a lid that allows for both because why not

I'm assuming it will fit non-ninja branded containers too. I use them on these without issue (affiliate link):

https://amzn.to/4ceRMNg

FIRJOY Replacement Pints and Lids for Ninja Deluxe 11-in-1 Creami Maker, Extra 24 oz. Containers - Compatible with NC501, NC500 Series (4 Pack - Blue, Pink, Green, Yellow)

Brand: FIRJOY