Disclosed is a combustor including a baffle plate having at least one through baffle hole and at least one fuel nozzle extending through the at least one baffle hole. At least one shroud is secured to the baffle plate and includes at least one piston ring disposed at the shroud. The at least one piston ring is configured to meter a flow of diluent between the at least one shroud and the at least one fuel nozzle. Further disclosed is a method for providing diluent to a combustor including providing a piston ring gap defined by at least one piston ring disposed at a baffle plate and a fuel nozzle extending through a through hole in the baffle plate. The diluent is flowed through the piston ring gap toward at least one airflow hole in the fuel nozzle.