It is a vital tool for assessing water clarity and light penetration. Designed with a 250 mm diameter, it features a four-segment configuration with alternating black and white sections to enhance visibility during measurements. Constructed from durable, hard-wearing plastic, the disk includes a lead weight to facilitate smooth lowering into the water. An approximately 15 cm high rod equipped with an eyelet allows for easy attachment of a lowering line, which is marked at 50 cm intervals for precise depth readings. Please note that the lowering line is sold separately.