This is a very nice original cast iron pump jack driver gear for a Monitor VJ pumping hit and miss gas engine. It may fit other models so please do your homework to be sure it fits your application. It measures about 3 3/4 inches in diameter and has a 1 bore. It is part number GA26 and is in excellent slightly used condition with no cracks, breaks, or repairs of any kind and is ready to go to work! It has a few very minor chipped tooth edges which will affect nothing. If yours is broken, missing, or repaired here’s a chance at an extremely nice one. It would also make a great spare on the shelf. The pictures tell the story. It would surely beat making one or trying to repair yours! I can be reached at 262 573 193 1 if you’d like to talk about it.