1. These are needed when using a HHO System or a test pipe.They are also used to lean out your vechicle for better gas milage. 2. The extender has a 7/8 hex head which is the same size as most O2 sensors and it makes them easer to install not like the straight sided extenders. 3. Fits all standard size sensors with a 1/2 Inch diameter tip.The size of the extenders is M18 X 1.50mm. 4. They are very easy to install by unscrewing your O2 Sensor from your exhaust then screw your sensor into the extender,and then screw the two pieces back into your exhaust. 5. Material: iron
