All Peli cases are made from a high impact structural copolymer polypropylene, with ABS latches, and use O-Ring sealing technology to make them watertight, airtight, and unbreakable in normal use. (Normal to you might be different from normal to us. They probably wouldn't survive being driven over by a 60 tonne main battle tank.) The automatic pressure purge valve allows for equalisation of air pressure, (without a purge valve the pressure differences caused by e.g flying would prevent you from opening the lid), but keeps water molecules out. All hinges use stainless steel rods, and the latches are double action, requiring less effort to open them.