4.5" x 3.8" When placed in a clean pool or spa, the Guardian ScumShield helps reduce the formation of scum lines along sides & improves filtration by catching unwanted substances before they enter your filter system!   Absorbs 40x its weight in body & suntan oils, suntan lotions, pollen, cosmetics, scum & more! 300% more surface area than the commonly used tennis ball Clog-free design does not get stuck in water lines In normal swim/spa conditions, ScumShield should last an average season To Use: Place in the pool skimmer or free float in spa. Flip to other side when full. When both sides are saturated, simply squeeze out, rinse & reuse!