During the day, these energy efficient, low-maintenance Atlantic Solars™ lights harness the power of the sunlight to charge their internal Lithium battery. At night they automatically turn on, emitting a bright light for your fence post line. Each Atlantic Solars™ light is made of Premium Heat-Resistant Plastic for years of use. With our Newest & Improved Solar Panels, an exceptional 3.2V Lithium Ion Battery, and 5 Ultra Bright LEDs, their efficiency and output are virtually unparalleled. The enhanced solar panels will ensure a superior charge, allowing for elongated illumination (up to 10 hours), while the 5 LEDs and 3.2V Lithium Battery will multiply the lights’ brightness for a total of 13.3x! The average mediocre light only has one single LED and an inferior 1.2V battery. These Atlantic Solars™ lights are undoubtedly of exceptional quality; they are one of the brightest and most efficient solar lights available. One Pre-Installed Exceptional 3.2V Lithium-Ion Battery Per Unit, LED: 5 Ultra Bright Amber LEDs, Can Last Up To 100,000 Hours Solar panel: New & Improved For Superior Charging Material: Premium Heat-Resistant Plastic Operating Time: Up to 10 hours (Depending on sunlight availability) Safe & Water Resistant Overall dimensions : 5.4″ (L) X 5.4″ (W) X 3.5″ (H) Two Mounting Bases (Inside Diameter) : 3.75 “X 3.75″ & 4 1/16″ X 4 1/16″ Fits on all PVC/Vinyl/Plastic/Composite and Wooden 4″x4″Posts & Deck Rails (Posts Measured Side To Side 4” or Less)