useing imported PE material Roling once mdding slippery inside and out side,no lichen nodirt,easy to clean in the barrel,healthy useing imported PE material Roling once mdding slippery inside and out side,no lichen nodirt,easy to clean in the barrel,healthy and anei-corrosion,suit for water treatment,environmental protection,water soften systerm,reagent feeder systerm and other fileds.. ...