The Periodic Products CuLator Ultra PowerPak 4.0 Metal Eliminator and Stain Preventer for Swimming Pools permanently eliminates copper, iron, manganese, cobalt, nickel, and silver. An included protector allows you to place the PowerPak within the pump or tie it to the reservoir of your fresh or saltwater pool. About Robelle Industries Since 1973 Robelle Industries has been providing superior, dependable, and affordable swimming pool products. They have painstakingly built a line of quality swimming pool products that include pool chemicals, pool accessories, and everything in between. Robelle is dedicated to finding new product formulations that meet superior standards of pool chemical efficacy and product durability so your pool is safe, crystal clear, and healthy. Ideal for use in waters with high metal or commercial pools. Removes 4.0 ppm of metals from 20,000 gal.. Includes protector allows to be placed in pump or tied to reservoir. Works in both fresh and salt water. Works up to 30 days.