2 Pack Plastic Copper Square Post Deck Fence Mount For Wood Posts (Wood or Composite Posts : must be smaller than 3-13/16" square) Sun Powered. No Wiring Automatic dusk-to-dawn operation, On/off manual over-ride switch Recharged by solar panel under sunlight Upper Base Dimensions : 4" (l) x 4" (w) - Lower Base Dimensions : 4" (l) x 5.5" (w) Wood or Composite Posts : must be smaller than 3-13/16" square. Hollow Vinyl Posts : inside opening must be larger than 3-15/16" square