This 8 x 1.25mm thread cleaning chaser tap from Checkered Flag Performance is designed to remove dirt, corrosion and debris from engine heads and blocks with 8 x 1.25mm threads. This chaser tap is specifically designed to clean threads without removing metal. Chaser taps are for cleaning and straightening existing screw threads, not cutting new treads or removing metal from the root of the screw thread, which can cause failure. Cleaning threads is a necessity for proper torqueing of fasteners. For the cost of this tool, you can't afford to skip this step of your engine build. This thread chasing tap is 2-3/4" long.