At 39.5mm in diameter, this Swiss Made midsize watch is the smallest model we’ve ever made with the ultra bright T100 tritium markers. The watch features 28 ultra bright T100 tritium markers that will glow for many decades. A combination of blue, green and orange tritium markers makes it incredibly easy to tell the time in any lighting environment. To ensure uninterrupted service, a reliable Swiss Made Ronda 505 quartz movement powers the watch. The movement also features a legible date display between 4:00 and 5:00. Constructed out of carbon fiber reinforced polycarbonate, this lightweight watch weighs in at only 3 ounces. The dial is well protected by a scratch resistant sapphire crystal with an anti-reflective coating. When your adventure involves water, this watch is ready to accompany you diving down to 200 meters. While in the depths of the sea, the unidirectional ratcheting diver bezel with a tritium marker will help you keep track of elapsed bottom time. Why do T100 watches last so much longer than T25 watches?The Isobrite T100 watches contain approximately four times the amount of tritium gas as the T25 watches do (i.e.: Luminox, Traser, MTM). The higher volume of tritium gas results in a much brighter visible illumination combined with a much longer life span of illumination. The Isobrite T100 watches will have a life span that is approximately twice as long as the T25 watches. Plus, at 25 years the T100 watch will have the same visible illumination that the T25 watch started out with. By that point the tritium in a T25 watch would have become fully decayed and barely visible. On the other hand, the T100 watch will continue to glow for approximately 50 years.