During the day, these energy-efficient lights harness sunlight energy to charge their internal battery. At night they automatically turn on, emitting a bright glow for your fence post line. It will decorate fences, entrances, deck rails One Pre-Installed 3.2V Lithium-Ion battery per light Light source: 5 Ultra Bright White LEDs Material: Heat resistance plastic. Operating Time: Up to 8 hours (depending on weather, regions and sunlight intensity available) Safe & Weather Resistant Dimensions: 7.5" diameter, 12" height On/Off switch (for testing and storage purposes- Must be turned on for initial use) *4 1/16" x 4 1/16" base (For 4 x 4 Hollow PVC/Vinyl/Plastic Posts)