BioGuard SilkGuard Complete Multi-Benefit 3 Inch Chlorinating Pucks are a revolutionary product exclusive to BioGuard. These chlorine pucks differ from traditional chlorine because the SilkGuard Technology actually softens the water by attaching to hard water components and metal surfaces, which protects your pool surface and equipment from scale, corrosion and staining. SunShield Technology offers protection from the sunlight while the Smart Technology helps the pucks last longer than traditional chlorine pucks. Also contains algae fighting crystals! This puck can be used in a skimmer, feeder, or floater. Use as Step 1 of the BioGuard 3-Step Pool Care System.