If you are purchasing a CorkSport Downpipe we recommend getting an O2 socket removal tool. This can save you a trip to the tool store when installing your downpipe. The CorkSport O2 sensor socket tool fits all Mazda O2 sensors. The offset wrench design connection point allows for multiple angles for those hard to reach spots. The offset socket design also allows for more leverage to be applied for the more stubborn sensors. The socket size is 22mm or 7/8".