We are required to pay for the cost of a Flat Rate Priority bubble sleeve for the return shipment from the host. The cost is $7.20 (last pkg I sent) & should not have a date on it because the swap host may miss the date deadline. I've heard USPS has a new stamp for Priority bubble sleeves but have yet to see one.
It is easier for me to pay the clerk for the stamps & attach them to the return bubble sleeve & put it in the pkg when I mail my charm pkg to the host because any weight is included in the price. Some swappers send stamps, hidden cash or a money order. Which ever fits your needs. Some hosts order the free bubble sleeves before the swap so some don't require you send the empty sleeve for the return charms.
We can mail to the host however we think it will get there in time, but if you mail another way, be sure to track it.
Note: Always put your charms in a ziplock bag with your name & address on the ziplock in case the bubble sleeve or other shipment form gets torn during shipment so USPS will know where to return it. Plus the host uses the ziplock to distribute your new charms & the charms are protected on their way back to you.
Hope this helps.
hugs,
dj