
These are made from five pieces of semi-glossy paper, with tape for hinges, and batting. Cheap, and easy. And, many of these small envelopes will fit into a drawer or tupperware. Another plus, as opposed to standard envelopes is that the body isn't squished, and the wings are already horizontal.
Yes, there are some drawbacks, but those I looked at hadn't removed much from the upper surface of the wings- it was negligible.
Each envelope is number, which is entered into a log book.
Strikes me as a great way to field pack specimens for later relaxing and setting.