Copper Top Solar LED Light 4" x 4" Post Caps for Bridges, Fences, Decks, & Posts No Wires, No Electricity, & No Hassles! Easy to install and maintain Light up your deck or porch day and night Two AA Ni-Cad Rechargable Batteries ensure longer lighting power up to 12 hrs of light Will fit on any 4" x 4" post only. The outside dimensions of a normal 4 x 4 measure 3 5/8 x 3 5/8