This is a small Pin which fits into the hole on an Esun/elegoo spool edge rim to stop the cardboard and rim sliding. its a snug fit and allows you to have just one set of 2 spool edges per spool if you have both brands. simply print on its back in PLA with no supports and push in place on the plastic cover side. note it will need rotating first to fit as the esun rims have a bigger hole diameter in them.

The esun spool has a 7mm diameter hole, the elegoo has a 5mm hole. This adapter / Pin is a stepped Pin with a 7mm then a 5mm pin.

its just a push fit. print one for each rim in PLA.