I still use them for ham radio QSL cards. They work everywhere that is a member of the Universal Postal Union (nearly all are). You can buy them online from Swi

I still use them for ham radio QSL cards. They work everywhere that is a member of the Universal Postal Union (nearly all are). You can buy them online from Swiss Post. They will mail them for free. https://shop.post.ch/en/packing-sending/sending-letters/registered-prepaid/international-reply-coupon/p/554094 https://shop.post.ch/en/packing-sending/sending-letters/regi...