Easy to assemble and can be combined to obtain the required installation height. Couplers overlap 1-1/2" when joined. Assembled length is 1-1/2" less than listed lengths. Size refers to the inside diameter of the pipe or fitting. The outside diameter of RV is approximately 1/2" larger. Type B gas vent. No. 3RV-18: Size: 3" x 18", Material: Alum Liner/Galv Steel Jacket, Temperature Rating: 550 F, Grade: UL Listed No. 103024: Size: 3" x 24", Material: Alum Liner/Galv Steel Jacket, Temperature Rating: 550 F, Grade: UL Listed, Pkg Qty: 1, Package Type: Box No. 3RV-36: Size: 3" x 3', Material: Alum Liner/Galv Steel Jacket, Temperature Rating: 550 F, Grade: UL Listed No. 3RV-60: Size: 3" x 5', Material: Alum Liner/Galv Steel Jacket, Temperature Rating: 550 F, Grade: UL Listed No. 4RV-18: Size: 4" x 18", Material: Alum Liner/Galv Steel Jacket, Temperature Rating: 550 F, Grade: UL Listed No. 4RV-36: Size: 4" x 3', Material: Alum Liner/Galv Steel Jacket, Temperature Rating: 550 F, Grade: UL Listed No. 4RV-60: Size: 4" x 5', Material: Alum Liner/Galv Steel Jacket, Temperature Rating: 550 F, Grade: UL Listed No. 5RV-18: Size: 5" x 18", Material: Alum Liner/Galv Steel Jacket, Temperature Rating: 550 F, Grade: UL Listed No. 5RV-36: Size: 5" x 3', Material: Alum Liner/Galv Steel Jacket, Temperature Rating: 550 F, Grade: UL Listed No. 5RV-60: Size: 5" x 5', Material: Alum Liner/Galv Steel Jacket, Temperature Rating: 550 F, Grade: UL Listed No. 6RV-18: Size: 6" x 18", Material: Alum Liner/Galv Steel Jacket, Temperature Rating: 550 F, Grade: UL Listed No. 6RV-36: Size: 6" x 3', Material: Alum Liner/Galv Steel Jacket, Temperature Rating: 550 F, Grade: UL Listed No. 6RV-60: Size: 6" x 5', Material: Alum Liner/Galv Steel Jacket, Temperature Rating: 550 F, Grade: UL Listed