At the heart of the Deepsea’s case is Rolex’s patented Ringlock system, which uses a super hard, nitrogen-alloyed steel central ring to internally support both the extra-thick sapphire crystal and the Grade 5 titanium caseback. While the Ringlock system is largely responsible for the overall increase in the case size of the Deepsea, it actually enables the watch to be smaller than it otherwise would be, had it were to follow a more traditional case design while still retaining its same colossal depth rating.The primary purpose of the Ringlock system is to reduce the amount of stress placed on the case of the watch. As pressure on the watch increases at greater depths, the majority of it gets exerted on the front and back surfaces of the watch. Since the nitrogen-alloyed stainless steel compression ring internally supports both the crystal and the caseback of the Deepsea, the amount of force exerted on the actual case itself remains relatively minimal. Additionally, as the crystal and caseback get squeezed together, with the majority of the force being supported by the internal compression ring, the front and back gaskets of the watch get pressed together, ensuring an extra tight seal.The caseback on the Rolex Deepsea consists of two components: an inner caseback made from Grade 5 titanium, and an outer, screw-down caseback ring that is constructed from Oystersteel (904L stainless steel). With a traditional, single-piece, caseback design, the entirety of the pressure placed on caseback gets exerted on the case of the watch itself, particularly near the threads. By separating the caseback into two components, Rolex is able to redistribute much of the force being exerted on the rear surface of the watch. The outer, screw-down ring performs the sole duty of keeping the inner, titanium caseback tight on the watch, while the nitrogen-alloyed steel compression ring ultimately supports all the pressure being exerted on the titanium case-back itself.
