Radium Replacement Filter, Microglass 6 Micron All replacement elements for the Radium fuel filter use anodized aluminum end caps that are laser engraved for easy identification and use an internal Viton O-ring for compatibility with all fuel types. All replacement elements for the Radium fuel filter use anodized aluminum end caps that are laser engraved for easy identification and use an internal Viton O-ring for compatibility with all fuel types.