The Stafix SXS features the improved solar panel technology that requires less sunlight for top performance. This unit is ideal for those who live in variable weather environments and want more confidence during the long dark winter months. This versatile solar energizer comes with an internal battery and is perfect if you're a small block holder or are looking to power a small run off where mains power is not readily available. Up to 21 days operation without sunlight. Can be installed on standard wood or t-posts.