Osburn 3500 Wood Insert (OB03510), EPA 2020 certified wood-burning appliance from the Osburn 2026 Tri-State Distributors price list (effective March 1, 2026). Extra-large insert rated up to 110,000 BTU/h at roughly 76-77% efficiency, with the blower included. 3.5 ft³ firebox accepts logs up to 22 in; one of the largest glass viewing areas in its category. Recommended heating area: 1,000 - 2,700 ft². Maximum burn time: 10 h. Required: select your Door Overlay and Faceplate Size and Faceplate Trim below — these are separate, required components priced individually and must be chosen to complete checkout; they are not included in the base price shown here.