These eyepieces with their huge apparent field of view not only gave the observer a panoramic visual experience, but they relax the eye so the observer could pay attention to subtle details for extended periods. These ultra-wide angle eyepieces played a critical role in the military for aiming at targets, and their long eye-relief counterparts helped reduce eye injury from recoil. Each 100° Series Nitrogen-Purged Waterproof eyepiece is internally sealed and purged with inert, dry nitrogen gas to prevent internal fogging, to halt the intrusion of fine particulates and fungus, and to maximize the life of the internal coatings. To make sure, every 100° eyepiece is tested by submerging them down to 1 meter of water for 30 minutes. All 100° Series eyepieces are fully multi-coated and edge-blackened to produce maximum contrast.