During the day, these energy-efficient Atlantic Solars™ lights harness sunlight energy to charge their internal Lithium Battery. At night they automatically turn on, emitting a bright glow 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, a 3.2V Lithium Battery, and 5 Ultra Bright LEDs, its output is virtually unparalleled. Its 2013 Solar Panels ensure longer illumination (up to 6-10 hours), while the 5 LEDs and 3.2V Battery brighten the light output by 13.3x! Atlantic Solars™ 4 x 4 Black Fence Post Caps One Pre-Installed 3.2V 300mAh Lithium-Ion Battery, Can Last Up To 2 Years LED: 5 Ultra Bright LEDs, Can Last Up To 100,000 Hours Solar panel: 2013 New & Improved For Superior Charging Material: Premium Heat-Resistant Plastic Operating Time: Up to 6-10 hours Safe & Weather Resistant Dimensions : 5.4″ (L) X 5.4″ (W) X 3.5″ (H) 1 Mounting Base (Inside Diameter) : 3.75 “X 3.75” (for Wooden Posts)