All your climbing friends ask to charge their phones from your Goal Zero battery the moment everyone gets back from camp. You'd rather they didn't take a billion climbing photos every time they go to the crag, but the Boulder 50 Solar Panel powers your battery while you're away, so there's no real harm. State-of-the-art monocrystalline technology in Boulder panels deliver more power per square inch than any other solar technology available, and Goal Zero wrapped it up in a rugged, durable, rigid, waterproof, and impact-resistant housing for protection from the elements.