... machine fit one screw size, which make the Screw Supplier stable and easy to use. Features:Models: 514, 517, 520, 523, 526 ... , 530, 5401,Small size, exquisite, easy to operate;2,High work efficiency, 4 times faster than the circular type;3 ... machine fit one screw size, which make the Screw Supplier stable and easy to use5,Various models for different type of screws ...