Schluter® KERDI-DRAIN FLANGE KIT 3" ABSThe 3" ABS bonding flange for KERDI DRAIN for larger drain line connections. While 2" is standard for most residential showers, some installations require a 3" connection, especially in older homes or when local code specifies it. Same fleece covered bonding technology as the 2" version. Your KERDI membrane bonds directly to the flange with thin set mortar, maintaining the watertight shower envelope all the way to the drain. 3" ABS bonding flange for