These are needed when using an HHO system or a test pipe. They are also used to adjust the air-fuel mixture for improved fuel efficiency. They are very easy to install by removing your O2 sensor from the exhaust, attaching the sensor to the extender, and reinstalling the assembly back into the exhaust. The extender features a 7/8 hex head, matching the size of most O2 sensors, allowing for easier installation compared to smooth-sided extenders. Fits most sensors with a 1/2 inch diameter tip. The extender size is M18 x 1.50 and measures 1.253 inches in length, with an internal diameter of 0.5175 inches. For additional clearance, multiple extenders can be stacked. Includes a tapered seat design—no washer required. Color: Silver Material: Iron Model: M18*1.5 Universal fit for any 18mm thread size Straight bolt-on installation, no modifications required Very easy to install Package Contents: 1 x Oxygen sensor extender Note: Lighting and display settings may cause slight color variations between the image and the actual item. Measurement may vary by +/- 1-3 cm.