JSP Manufacturing 8 Pack New Fence Post Plastic White Caps 4X4 (3 5/8") Pressure Treated Wood Made In USA 8 Pack New Fence Post Plastic White Caps 4X4 (3 5/8") Pressure Treated Wood Made In USA FC-4x4-WHITE-08 THE EXACT INSIDE DIMENSION OF THIS CAP IS 3 5/8" X 3 5/8". Brand JSP Manufacturing