Sensus SRII 5/8 x 3/4 measuring chamber is a suitable synthetic polymer and is not casted as part of the main case. All piston assemblies are interchangeable in all measuring chamber assemblies of the same size. The measuring chamber piston operates against a replaceable control roller, allowing for repair to AWWA standards. The control roller rotates on a stainless measuring chamber steel pin, to provide added strength, wear resistance and corrosion resistance. There is a elastomeric seal or seals between measured and unmeasured water, preventing leakage around the measuring element.