The format is a single size, 230 x 152 mm, calibrated for a service keyring and what usually travels with it: an access badge, a site card, a folded instruction sheet. This is not a document pouch - for a file or mail, the format of a universal secure pouch is better suited, and a laptop belongs to another range altogether.
The front panel is clear, and that changes the way the job is done. The recipient counts the keys through the wall before breaking the seal: if the count is wrong, the dispute opens while the evidence of integrity is still intact. With an opaque pouch such as the one intended for precious items, you have to break it to check; here you check, then break.
The zip locks with a single-use T2 seal. A seal is not a padlock: it does not resist a tool, it proves that someone got in. Numbered, it becomes a traceable reference in a log. If you need to close a keyring without putting it in a pouch, the key-fob seal covers that case differently. The pouch also shields the keys from knocks and damp in transit, and the manufacturer states an antimicrobial treatment on the lining and locking chamber - an argument that carries weight on an item handled by everyone on a shift handover.