I originally ordered two of these for lifting 600lb+ steel sheets onto my plasma table. They seem to be very good quality. I ordered two more just for a safety factor for stability when lifting the thickest material. The first two units were reversed, ie on position and off position were reversed and would not function. I quickly realized I just needed to flip magnet to reverse polarity. Just placed unit on steel and with vice grip pliers and handle removed, I turned magnet 180 degrees. Work perfect now. Evidently some are assembled backwards at factory but it's an easy fix. Great product, very good price. Must have for every fabrication shop