Suburban Furnace Vent Extension 520973 (NT/P Series) 3-1/8 to 4-7/8 Inch Compatibility: Suburban NT-24SP/ NT-30SP/ NT-34SP/ P-30S Length (IN): 3-1/8 Inch To 4-7/8 Inch   Kit Includes: Cabinet Back- 101230 Exhaust Extension Tube- 050996 Intake Extension Tube- 050995 Screw #10 x 3/8&quo... See More