O-z Gedney OZ-Gedney EF-100 Type EF Concrete Slab Electroform Straight Conduit Insert, Size: 1 IN, Malleable Iron, Finish: Zinc Plated, Dimensions: 2-1/2 IN Base Diameter X 3-5/16 IN Base Across Flats X 1-5/8 IN Height, Third Party Certification: UL File Number E-11