Solar rock lights set of 4 are the brightest of the solar lights from our range. solar rock lights set of 4 are designed to cast a bright beam of light on plants, entrance and pathways. Sun light is stored in the built-in rechargeable battery and used to light up the lamp at night. With an auto environmental light sensor, no manual switching is required. It lights up automatically at dusk, lasting at least 12 hours till dawn. solar rock lights set of 4 are durable, and can last for more than 5 years and require no maintenance once installed. The solar panel can last for more than 20 years, but it is advisable to replace the rechargeable battery every 2 years for optimum brightness.