ASTRO PNEUMATIC 1-5/8 to 4-1/4 Exhaust Pipe Stretcher Kit, Metallic The ASTRO PNEUMATIC AST-78835-06 Exhaust Pipe Stretcher Kit is an impact-driven, heavy-duty expander designed for fitting smaller exhaust piping and creating secure exhaust seals. This kit provides a comprehensive solution for expanding exhaust pipes, ensuring precise connections and optimal exhaust system performance.