Heavy-duty cylindrical knob sets, designed for use in high traffic areas such as office building, schools, churches, restaurants, retail stores and warehouses, complies with ANSI A156.2, Grade 2 (400, 000) cycles, UL listed for 3 hr fire door. Door range of 1-3/8 to 1-3/4 in. Backset of 2-3/4 in standard. Commercial and Residential. Indoor and Outdoor. Fits standard 161 door prep, Schlage C keyway, keyed different, includes two nickel silver keys.