These corrosion-proof 4" PVC Rain Skirts 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. Overall dimensions are 6.875" diameter and 4" long. Socket depth is 1.75". NOTES: Fittings are triple bead welded. Pictures are to represent style of fittings only; color is gray.