The largest of the Fenix 6 watch family, the Garmin Fenix 6X Pro packs big features and bigger battery life into a low-profile timepiece. Garmin’s Fenix 6X Pro measures 51mm in diameter, so you never have to squint to read the face, and with a big case comes big battery life: Garmin says you’ll get up to 21 days in smartwatch mode and even longer in more efficient modes. Garmin Fenix 6X Pro battery life: Smartwatch: 21 days GPS: Up to 60 hours GPS + Music: Up to 15 hours Max Battery GPS Mode: 120 hours Expedition GPS Activity: 46 days Battery Saver Watch Mode: 80 days A Fleet Feet tester put the battery to the test. In our Garmin Fenix 6 review, a tester says he was able to use the watch for regular training for nearly three weeks on a single charge before the battery ran out. The newest Fenix comes with the same wrist-based heart rate monitor and Pulse Ox sensor as the smaller Garmin Fenix 6S Pro and Garmin Fenix 6 Pro, and it uses the same durable Corning Gorilla Glass 3 and rugged stainless steel or Diamond-like Crystal-coated steel bezel. Garmin engineers tested the Fenix 6X Pro to U.S. military standards for thermal, shock and water resistance. Those tests yielded a 10 ATM water rating, which means it can withstand water pressures equivalent to 100 meters. Behind the lens is a color 1.4” display that’s 36 percent larger than previous Fenix models and other Garmin watches. The color highlights topographical and ski maps, adds contrast to turn-by-turn navigation screens and lets you easily see your route. With new safety, tracking and incident detection features, the Garmin Fenix 6X Pro will keep you in touch while you train harder—and smarter—than ever before.