2 1/2" (64mm) afterset. Installed either before or after concrete pour to create activation from duct (minimum concrete depth of 2 1/2" (64mm)). Requires 6 1/2" (165mm) core drilled hole in concrete and 2 1/2" (64mm) diameter hole in duct. Grout fill required around afterset once installed to fill voids and support fitting flange. Attaches to duct using locking tabs. Extensions can be attached to increase height. Aftersets include alignment clip and mudcap. Zinc