McDonald® Plug Valve Corporation Stops are precision machined to assure a perfect match between the plug and the body. This same machining precision carries over to the threads to assure McDonald's high quality. Corporation stops come standard with 360 deg operating head. Use only smooth jawed wrenches on corporation stop bodies and position the wrench only on the flats provided on the bodies. Also position your wrench as close as possible to the threads being tightened to avoid excessive strain or bending moment on the body. They are made in the United States of America and are manufactured to meet or exceed the AWWA C800 (latest revision) standard, except where noted.