Clear Travel Bag

Airport security defines this bag, not a designer. Carry-on liquids have to travel in containers of 3.4 ounces, or 100 ml. All of them must fit inside a single resealable transparent bag holding about a liter, one per passenger. In practice that means a pouch near 7 by 8 inches. Container size is what gets judged rather than contents. A half empty 6 ounce bottle is refused at the belt while a full 3 ounce one goes through.

Construction is thin by design. Most are a single welded sheet of clear vinyl or thermoplastic polyurethane, called TPU, closed with either a slide seal or a light coil zip along the top. TPU stays flexible in cold and yellows more slowly, while vinyl costs less and cracks at a fold once the temperature drops near 40F. Tinted or frosted panels defeat the purpose, since a screener has to read the contents through the wall, so keep the plastic really clear rather than smoked.

A flat cosmetic pouch shares the footprint and hides everything, which makes it useless at a checkpoint and better in every other setting. Hanging toiletry bags often include one of these on a snap, and that pairing saves you unpacking twice in a queue. Dopp kits and train cases are checked baggage territory, because full size bottles cannot pass the rule at all. Keep this pouch at the top of your personal item rather than buried under a laptop, since it comes out at every screening.

Anyone flying with cabin baggage only needs one, and weekly flyers should keep it permanently packed with duplicates so nothing gets forgotten at home. Some airports now run scanners that let liquids stay inside a bag, though the rollout is uneven between countries and even between terminals in one city, so pack to the strict version and treat any relaxation as a bonus. Fill it, seal it and turn it upside down over a sink to test the closure. Replace it when the plastic clouds.