Monessen DIS Propane Vent Free Fireplace Insert. DIS33PVG. Built-in Fireplaces. This Monessen DIS Propane Vent Free Fireplace Insert is the perfect way to bring your existing fireplace to life again, without the hassle of making a real wood fire. This insert will fit most standard fireplaces with a minimum opening of 24 inches high and 33 inches wide. This insert features the Triple Play Burner System that produces 28,000 BTUs. This System includes: Deep ember bed, Charred Timber logs, removable unitized bottom louvers, thermostat blower (135 cfm), 18 inch flex line with on/off shut off valve and volcanic rock.