These versatile post caps can be used on your patio, deck, fence, or pathway. Removal of the base allows easy installation to nearly any 4" x 4" post. The included 1.2V 600mAh AA Ni-CD battery will be recharged every time the solar panel absorbs sun light. These lights feature a unique mechanism that allows you to turn it on once and never have to worry again. No additional wires or power source are needed. It is recommended to install these post cap lights in an area that receives sunlight for 6 to 8 hours a day. Product Dimensions: 5.75" x 5.75" x 4.5", Base Dimensions: 4" x 4". Post Size Fitting; for Wood or Composite Posts must be smaller than 3-13/16" square; for the Hollow Vinyl Posts the inside opening must be larger than 3-15/16" square