This 3/4 Inch BSP Metal Filter Gauze Washer has an approximate diameter of 1 inch and is used for preventing debris from entering washing machines, showers and other water supplied appliances 3/4" Gauze Filter Flat Washer - IMPORTANT NOTE, MOST PLUMBING PRODUCTS ARE STATED AS BSP IMPERIAL THREAD MEASUREMENT WHICH MEANS THAT ACTUAL DIAMETER OF THE THREAD SIZE IS APPROXIMATELY 1/4 INCH LARGER THAN THAT STATED IN BSP TERMS. FOR EXAMPLE THIS 3/4 INCH BSP THREAD ACTUALLY MEASURES APPROXIMATELY 1 INCH IN DIAMETER