Available at any post office, these are used in place of SASEs when mailing to a foreign country.

Coupon purchased in Canada or other member country of the Universal Postal Union that may be exchanged in any member country of the Universal Postal Union for the minimum postage payable on an international unregistered letter. (coupon-réponse international)

A redeemable certificate issued by member nations of the Universal Postal Union to provide for return postage from recipients in other countries. IRC's are exchangeable for postage at a post office.