Korky R528 Replacement Fill Valve Cap Assembly for Korky Fill Valves Rubber Made in US Replacement cap for Korky QuietFill Fill Valve Chlorazone diaphragm Also fits Hunter 528 and TOTO fill valves Committed to Quality Made in USA Longest Lasting Products Quick &amp; Easy to Install Bacteria, chloramines, chlorine, city water treatment, hard water, well water and rust