ASMD You need to know how much plastic each model uses in weight - grams. Your slicer will tell you this. The roll is 1000g. So then you can work it out

ASMD you can use the official Xiaomi gateway. Set it up with the app, add all your Xiaomi zigbee devices to it. There is a 'secret' developer mode in the app that reveals its id so you can link it up with Home Assistant. Then home assistant can see all the devices that are connected to the Xiaomi gateway.

ASMD the rings I received were actually 66mm outside diameter, so either the listing is wrong or I received the wrong items