OPELLA Torbeck 1/2" Side Entry Filling Valve Opella code B801A - 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 1/2 INCH BSP THREAD ACTUALLY MEASURES APPROXIMATELY 3/4 INCH IN DIAMETER