I've only done three swaps. In the first I used the little containers that most fly shops have for collecting your flies--you know, kinda like the salsa containers at Baja Fresh. Then, I got the little Plano multi-compartment containers from Walmart for about $1.50. Each time, I've sent my flies in a padded envelope along with a self-addressed, postage paid, padded envelope. I think total postage was a little over $1.00. Honestly, I forgot what the padded envelopes cost, but I picked 'em up at the local grocery store. I like using the Plano containers, especially for dries.