Monster Hardware is a great company that listens to their customers. Monster millers wanted a larger hopper, so Monster Brewing`s head hopper designer came up with an extension to please all of you. Total capacity is up to 39lbs, perfect for all 10 gallon batch sizes, and a single hopper fill. Made of the same durable materials, and bolts directly onto all of our existing hoppers with a perfect fit. Sold as an add-on to your new or existing hopper. Because the parts are built very accurately, the holes line up perfectly. The whole works assembles easily in minutes with the included #8 machine screws, washers, and nylon insert lock nuts. We include nylon insert nuts so they wont vibrate loose while milling. The hopper mounts to the top of the mill using the included ¼-20 half inch long mounting bolts. If you had an erector set when you were a kid, the process should bring back fond memories. (hopefully!) The only tools necessary for assembly are a Philips screwdriver PLUS an 11/32 box end wrench, socket, or a pair of pliers