This O2 cel fix actually has a miniature catalytic converter built inside and will help get rid of that annoying check engine light you get after modifying your exhaust or removing your catalytic converter, and sometimes even when installing a high flow catalytic converter. Don't take a chance on using an extension only as often they do not work, this is a real mini Catalytic Converter built into it. This O2 cel fix with miniature cat will trick your ECU into thinking the stock catalytic converter is still installed. When you remove your catalytic converter, your post O2 sensor will see higher temperatures and greater flow of unburnt fuel. As a result this will throw check engine lights (Cel, SES, DTC) typically the error codes will be P0420 (Catalyst System Efficiency Below Threshold Bank 1) and/or P0430 P0420 - Catalyst System Efficiency Below Threshold Bank 2). For OFF ROAD use only Specifications: Weight: 90G Size: As the picture shown Material : Metal Thread: M18 X 1.5 Color: As the picture shown Package: 1 Piece(with catalysts) Notes: Please allow 0.1-0.5cm difference due to manual measurement. Please check carefully to make sure whether the item matches to your vehicle or not. The color of the actual items may slightly different from the listing images due to different computer screen, thanks for your understanding. Instruction is not included.