This HERMS (Heat Exchanged Recirculating Mash System) will allow you to take full control of your mash temperatures. Installed in a hot liquid tank, water is heated to mash temperatures with wort circulated from the mash tun, through the Herms coil, and back into the mash tun. This circulation allows you to maintain, raise, or lower the mash to desired temperatures. The large coil fits 15 to 55 gallon kettles.