BIG D TOILET BOWL RIM HANGERS WITH NON-PARA BLOCK fit most toilets and deodorize up to 1,500 flushes (30 days normal operation). The compound inside gradually dissolves, coloring the standing bowl water a fresh aqua as it imparts a nice fragrance. Replace when the water is no longer colored. Blocks are acid-free and water-soluble. Deodorizer Type: Toilet Bowl Block; Scent: Evergreen; Color(s): White.