Sioux Chief Mfg 884-ATMPK 4-Inch by 3-Inch Total Knockout Closet Flange Knockout will not break apart and cannot fall down drain pipe Corrosion-resistant 430 stainless Steel swivel ring is engineered for maximum strength Holds five floors (22 psi) for head test Proven performance, improved design Closet flange Knockout will not break apart and cannot fall down drain pipe Strong, corrosion resistant stainless steel ring eliminates cracked flange Easier installation, no need to hold knockout while hammering 3-Inch hub and 4-Inch flush to floor