Set of twelve 5 inch diameter (15.7" Circumference) stovepipe heat exchanger / radiator rings that reclaim heat from the hot stove pipe and radiate the heat into the room. They make close contact with your stack / pipe to draw more heat out of the pipe. They increase the area of heat dissipation just like the aluminum fins on a motorcycle engine. Heat is conducted into the radiator loops where the heat is transferred into the air. They are widely used as stovepipe heat exchangers that reclaim heat from the hot stove pipe and radiate the heat into the room. You get one lot of 12 radiators. They are made of 28 gauge high thermal conductivity aluminum, 1 ½ inches wide. They attach quickly and easily to your pipe or exhaust stack. No screws or tools needed. The ends lock into each other. It takes about 5 minutes to attach all 12 radiators. They will last a lifetime. They never need maintenance. They are guaranteed to draw more heat from the pipe. You may put on as many bands as you have room for. One set of 12 bands covers 18 linear inches of exposed pipe. ***PLEASE*** measure your circumference with a flexible tape or string. (Circumference divided by 3.14 = diameter.) See other listings for more sizes. (3, 3.6, 4, 6, 7, and 8 inches. NOTE: The length of pipe in the picture is not part of the sale.