Engine builders and mechanics, this is the classic Flex-Hone from Brush Research. It's a flexible ball hone used for the final finish or 'deglazing' of cylinder walls in an engine block. This specific model has a 4-5/8 inch (118mm) diameter, which is the size of the cylinder bore it's designed for (it can also work on slightly smaller bores). The abrasive balls are made from 180-grit Silicon Carbide, which is great for a smooth finish. The beauty of the Flex-Hone is that it's self-centering and self-aligning – you just chuck it into a standard 3/8\ or 1/2\ drill, run it in and out of the cylinder a few times, and you're done. It creates a perfect cross-hatch pattern that helps new piston rings seat properly and retain oil. It's also fantastic for deburring and polishing other metal tubes or bores. Made right here in the USA. An essential, easy-to-use tool for any engine rebuild or cylinder repair job.
