Extra Cool — special propylene glycol-based coolant for laser coolers. Volume 3.8 liters. Suitable for HanLi, S&A coolers and other laser cooling systems. Frost protection down to -20°C. Protection against corrosion of internal components of the cooler. Prevents the formation of algae and bacteria in the cooling circuit. Extends the life of the Raycus and JPT laser source. Usage: do not mix with distilled water. Change every 6-12 months, or before the winter season. Important for the winter season — if the laser is in an unheated space, Extra Cool is a must to protect against freezing.