A COBB Sizing Tester is an instrument used to measure the water absorbency or the water resistance of paper or paperboard. The Cobb sizing tester consists of a circular metal ring or clamp with an absorbent pad underneath and the instrument also includes a reservoir for water and a precise means of controlling the water flow. The test measures the time it takes for the paper to reach a specified level of water penetration or the amount of water absorbed by the paper within a specified time. COBB Sizing Tester helps assess the suitability of paper and paperboard for various applications, such as printing, packaging, and labeling, where water resistance or absorbency is important.