This is a NOS, new old stock cast iron piston 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 4 3/16 inches long. It is 0.010″ larger than 3 1/2″ in diameter and is stamped from the factory as such as can be seen. The wrist pin is about 2 1/2 on center from the top of the piston. It is in excellent unused condition with no cracks, breaks, or repairs of any kind and is ready to go to work! It came from the estate of an early engine collector and I’m pretty sure he got it directly from Monitor or a local hardware store or implement dealer when they cleaned out shop decades ago. If yours is broken, missing, or repaired here’s a chance at a new 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.