Patco Odour Blocks contains top quality Paradichlorobenzene (PDB), premium grade dyestuffs and perfumes. The purpose of these blocks is to deodorize. They are air-activated and do not dissolve in water. This product does not deodorize the flushing water and urine but rather then dissolves into the atmosphere. Each time the urinal is used the Patco Odour Blocks dispenses specially formulated cleaning agents. This helps maintain the drainage system, providing a cleaner and odour-free washroom. Now with our new special splash back reducing design. Excellent for washroom urinals, toilet bowls, drains and dirt bins.