McFarland Cascade Terratec Luminous Plastic Solar Post Cap, Black, Fits 4x4-Inch Post LED lights are a highly efficient source of light compared to other types of bulbs. Adds a finishing touch to any 4 in. x 4 in. post On average, an LED light will last approx. 100,000 hours or more Great for hiding any irregular or out of square posts Protects the post from excessive water penetration.