There's no greater assurance than being able to see the o-ring seal. Simply close the two double-passivated stainless steel locking lid snaps, and see the o-ring form a solid black, watertight seal. Ikelite products are designed, built and tested in the USA. We use locally sourced, top-grade materials. Our housings are built by hand and individually tested for fit, function and waterproof integrity. We back our products with over 50 years of experience and service within the dive industry.