1/4" NPT Mini filter-reducer piggyback duo is recommended when space is a problem. Duo offers most of the same features as the full size units. Preassembled with 0-160 PSI gauge # 1189. Piggyback mini FR Duo is ideal for use in compact air flow applications. Maximum pressure 150 PSI and maximum SCFM of 21. Preassembled with Milton® #1189 gauge.