Made by the company that pioneered high quality cases; good in 1975, better today. These SR (Structural Resin) Cases are the standard in waterproof, airtight cases. New sizes are introduced and design improvements are made every year. The latest in impact and temperature resistant materials are used. SR cases meet the most demanding requirements for carrying cases. Drop tested and meets MIL-4150H-J humidity and immersion tests. Case Material is ultra high impact structural copolymer polypropylene foamed core.