This is a real nice original steel drive coupler for an International Harvester rotary magneto for a tractor. It is in excellent condition with no cracks, breaks, or repairs of any kind. This was used with the E4A magneto as used on the 8-16, 10-20, 15-30, 22-36 tractors and possibly others. It measures 1 1/4 inches long and 1 1/2 inches in diameter with a 1 inch center bore. The lugs and slots are 1/4 x 1/4 inch. I believe this piece is ready to be used on a magneto. If you need one for any reason here it is. The pictures tell the story. It would also be a great spare on the shelf. You'll like it. I can be reached by phone or text message if you'd like to talk about it. Good Luck.