This Medium grade coal load is designed to fit the MTH Premier 4 bay hoppers. The inner dimensions of the car that this load fits are 2 1/4" wide by 11 3/4" long. Our manufacturing process incorporates properly sized coal particles into the prototype model prior to molding. Our coal loads are made from black high impact rigid polyurethane foam. These are lightweight and won't affect how your car tracks on your rails. All of our loads are ready to place in the well of your car right from their package. This load will not dry out, experience glue/epoxy failure, or make your car top heavy. Nor will it sink into the body of your car from under its own weight after three years of use like many crushable foam, glue, and painted sand loads that others call coal.