Ace Race Parts 74001 M18 x 1.5 O2 Sensor Bung - Coped for 1.500-2.500 OD Tube - CP2 TitaniumAce Race Parts 74001 M18 x 1. 5 O2 Sensor Bung Coped for 1. 500" 2. 500" OD Tube CP2 Titanium CP2 TITANIUM O2 SENSOR BUNG M18 X 1. 5 THREAD The Ace Race Parts brand of metric Oxygen (O2) Sensor Bungs is precision machined using solid CP2 Titanium bar stock and work with all standard O2 Sensors that use a M18 x 1. 5 thread. This specific O2 sensor bung fitting is coped to fit 1. 500" OD to 2. 500" OD tubing; however, it can easily work with other tube