These corrosion-proof 18" PVC couplings are for the construction of exhaust ventilation systems. PVC material compounds used in the manufacture of these duct fittings conform to PVC 1120, ASTM D-1784, Type 1, Grade 1, Cell Class 12454-B. Couplings are "sleeve" type. Service temperature is 33°F to 140°F. NOTES: Fittings are triple bead welded. Pictures are to represent style of fittings only. Couplings are 4.5" in length.