4" center. 12550 ceramic disc cartridge design. Water/energy saving aerator. Hook-up supplies included. 1/2" IPS inlets. Inlet shanks will accept 3/8" ball nose connections. Third party certified to ASME A112.18.1/CSA B125.1, ICC A117.1 and all applicable requirements referenced therein, certified to ANSI/NSF 61/9. Complies with California Proposition 65 and with the Federal Safe Water Drinking Act. 1.5 gpm.