We take our smartphones everywhere. More precisely, we use them everywhere! And this Hand Warmer helps keep your fingers nimble and warm while you're passing time on it in the tree stand waiting for your trophy to come into sight. The Hand Warmer has reliable ThinsulateTM Insulation and scent protection, just like your favorite hunting gear has. But it also has a "window" for you to use or view your smartphone, MP3 player or GPS while using it inside the Hand Warmer! Sheer Genius!