Selkirk, formerly known as Metalbest or Metalbestos, are ideal for venting residential heating appliances burning wood, #2 oil, and natural and liquid propane gas. Selkirk is specifically designed for today's modern, high efficiency "airtight" wood stoves and for use with gravity (natural draft), non-positive internal pressure venting only. The MCS is usable on any appliance having a power burner (such as an oil furnace) if that appliance operates with neutral or negative draft at its outlet. Non-residential appliances which may cause positive pressure in the chimney should use a Selkirk Commercial Model PS or IPS system. Please Note: All Stove & Chimney Pipe is chosen and classified by the inside diameter. If your flue has a 6" Inside Diameter you will choose from the 6" Stove and Chimney Pipe categories.