The Unbreakable Core: Dissecting Nokia XR21 Durability Through an Extreme Conditions Gauntlet The very premise of a rugged smartphone invites skepticism. Marketing claims of “military-grade” toughness and waterproof superiority often collide with the messy, unpredictable reality of field work, outdoor adventures, or simply a clumsy moment. The Nokia XR21 enters this arena not just with