PlumBest C51300R 3-Inch PVC Closet Flange Less Knockout Long shank; six screw holes 3-Inch fits inside 3-Inch Schedule 40 DWV pipe Extra-thick flange with short slots for extra strength For 3-Inch units cut pipe 1/8-Inch below floor and remove concrete so unit will be flush 3-Inch has 4 closet bolt slots