This is a Magnetic Copper Backing plate used as a welders aid in plug welding holes in sheet metal , the back side of a seam or anytime you need to fill a gap with weld.. The weld does not stick to the copper and adds as a heat sink to absorb heat and prevent warpage. The copper plate is 1/8 to .100 thick and varies in size in width most are 1 1/2 x 3 in  , the size varies and have four.250 diameter Magnets to hold hand free.This would be a great addition to anyone tool box. I make these myself so they are not made in a factory overseas. USA shipping only Thank You