An envelope produced by the Jiffy Packaging Company, padded internally with bubble-wrap to provide protection for its contents. They come in a wide variety of sizes. If you're in an office right now, there'll probably be one within a two-metre radius. Jiffy Bags are very useful for sending CDs and cassette tapes through the post on those occasions you don't need to box them up as a parcel. I'm looking at a Jiffy Mailmiser MM1 right now (it's on my desk, hence the node) and it says it was created with paper from sustainable forests, which is another point in their favour.