The stainless steel coil is designed to be used with a water-cooled system. Chilled fresh water is pumped through the coil, which should be submerged in the nutrient reservoir. The fresh water used to cool the reservoir does not mix with the water in the reservoir. Includes 10 ft of coil and 20 ft of 3/8 in heavy-duty tubing, 1/2 in and 3/8 in brass hose barb adapters and stainless steel hose clamps. Requires chilled water flowing through it to operate.