Hello guys i made this pendant for your pet collar which contains an nfc chip and people can scan it to get your information if they find your lost pet. You can write the tag easy with an app mentioned below so when people scan it with their phone (like contactless pay) it shows the info you want them to see to contact you about your lovely one. 
*The keychain hole is big because I used those plastic clip keychains because its more stable, doesn't turn all that much and won't break so easy as the common ones with the metal ring. 
if you want to use the rings design then go to objects (see last picture), find the cylinder and change it to something like 3mm. you can also move it around, i kept it as a negative part in the slicer so you can play with that if you need to. 
Putting in the nfc tag: A pause is already added so the print will automatically pause when you need to place your nfc tag, then simply press “resume printing” on your printer. 
Make sure you get good nfc tags that work with both android and IOS and make sure they are 25mm, otherwise you will have to go into objects and do what i said above about the keyhole. I used ones that have adhesive on them too, so they dont move mid print before they are sealed. 
*I used the phone app ‘NFC Tools’ with the orange logo, plenty of youtube guides on how to use them and it's super easy.

DO NOT change the print scale entirely, you have to go into objects, find the main part and change only X and Y axis or it wont work. Then adjust the other parts position if you need to.

DO NOT click repair non-manifold edges because it will ruin the print.