Fewer wall penetrations than standard single-unit venting;Reduced install cost with easy to install non-powered kits;Flexibility of using PVC or polypropylene vent material;Approved for use with BTH 120, 150, 199, 250, 300, 400 and 500 Cyclone models and BTHL 150, 199, 250, 300, 400 and 500 models;Approved for side wall (horizontal) vent applications only;50 Feet maximum equivalent length of straight pipe common vent and elbows