Boardwalk NUS Urinal Screen w/Non-Para Cleaner Block, Green Apple (Box of 12) Deodorizes, cleans and prevents scale buildup. Water activated. Every flush tints the water blue, while healthy bacteria eliminate odors, fight bacteria growth and maintain drain lines. Screen traps debris. Lasts up to 1,5 flushes. Deodorizes, cleans and prevents scale buildup. Water activated. Every flush tints the water blue, while healthy bacteria eliminate odors, fight bacteria growth and maintain drain lines. Screen traps debris. Lasts up to 1,5 flushes.