Chromium Steel: Each screw extractor is high hardness chrome steel and has been heat-treated for durability Every etching size is very clear with high visiblity for quick identification Powerful: This bolt extractor is designed with internal thread that has reverse spirals grooves designed can be occluded to provide maximums Each surfaces is precisions machined and resistant to Multi-Size: The screw extractor sets ranges from 1 / 8 inch ( 3.5mm) to 7 / 8 inch ( 23mm) It has 1 / 32 inch increments and come with a storage box, which is very to store these screw extractor Wide Application: This bolt remover is easy to remove the and stripped screws, bolt and slip teeth, or can be used with a variety of square drive wrenches for a wide ranges of applications Upgraded Bolt Extractor Kit: Compared to the old extractor, this new screw extractor kit does not require the socket to be placed on the hexhead before spanners is used It ' s more, The 3 / 8 inch drive design makes the screw removal device suitable for hand tools, electric or pneumatic tools, Manufacturer: Kaeltsyn