Cornell Dubilier Electronic’s transitioned the MPF series from a steel housing to an aluminum case called out with the “A” suffix in the part number, for example 32FD3702A-F
21FB4420 ==> non-RoHS, steel case
21FB4420-F ==> RoHS compliant, steel case
21FB4420A-F ==> RoHS compliant, aluminum case. ( “A” indicates aluminum case)