The ThermoBarrel™ Mash Tun is a fully insulated, stainless steel mash tun. For those brewers looking for an alternative to modified plastic coolers , there's finally an option. The stainless steel serves several benefits. The foam insulation design gives the tun heat retention comparable or better than most plastic coolers after stabilization. It's long lasting, it prevents any leaching of plastics, and it's easier to clean.