Selkirk; Selkirk DSP 8″ Double-Wall Stove Pipe Telescoping 12″ – 18″; 77525 Selkirk DSP 8 Double-Wall Stove Pipe Telescoping 12 – 18. Includes: A finishing band. Features: Material: 430-alloy stainless steel inner wall, steel outer wall. Limited Lifetime Warranty. Use with SuperPro and Ultra-Temp factory-built chimney. Reduces clearances from 18 to 6 for both walls and ceilings. Specifications: Overall Dimensions: 8 (W).