Post Cap lights Solar Powered: This solar post caps fits exact 3.62" size post. The solar LED post cap light comes with a bracket, also suit for 3.5x3.5 4X4 5X5 6X6 wooden post. If your pillar is 3.62", you just need to tighten the screws directly from the side. if the post size is smaller or larger than 3.62 inch , you can install with the bracket. Note : Please mind the size before buying. Auto On/Off: The solar post light is built in photosensitive component of the solar post cap, which makes the light auto on at dusk for decoration and lighting, and auto off at dawn for charging at daytime. It will steady for all night after full solar charged.