You will make at least 15 envelopes for your partner.
For size I suggest about C6 (114 x 162 mm or 6.4 Ã— 4.5 in) or DL (110 x 220 mm) as this should be able to send as "regular" letter in every country. It doesn't have to be exact this size.
Any paper is acceptable (maps, calendars, magazines, scrapbook paper, etc.) as long as it is sturdy enough.
Make them nice and decorate if needed. Try to vary the patterns/colors.
Lining of the envelopes and double sided tape on the flaps is optional.
Store-bought envelopes that are decorated by yourself are NOT acceptable.
For those with low ratings:
1-ratings within the last 12 months are not acceptable (only very few exceptions, contact me before joining). 1-ratings from active swappers are not acceptable at all (except the swapper is known for unfair ratings).
Re-solve your old swaps before joining new ones!
For people living in Europe:
See my profile for groups for swaps within Europe.