I put 3 chips with bristol/poster board in #8 envelopes. I haven’t found my scale yet after moving, so I brought it to the post office and used the one there. Came out to 28 grams exactly.
The lady was feelin up my envelopes and asked me “Is there stuff in here or anything? If there is, you have to fill out a customs forms” I replied “No, they’re just 3D cards” got em stamped and sent out.