The cast iron master cylinder brakes are suitable for Chevrolet 1981-1996, GMC 1981-1996. The bore diameter is 1-5/16" which equal to 25.8mm. The thread diameter of the outlets is 1/2-20 for the rearward one and 9/16-18 for the secondary one. The OEM number is MC39435, which is a replace part for OEM 14066425 and 174-838.
