The Sairset 15# is a air-setting refractory mortar that can be used with insulating firebricks, firebrick and materials that need a high temperature air-setting mortar. The maximum service temperature is 2900 F. This product weighs 15 lb./7 kg. *Please note: this product comes premixed with water already added. The required material is: 350-400 pounds per 1000s 9" straight bricks or 3 bricks per pound. We are now shipping in a cardboard box to avoid UPS special handling charge of $8.00 per pail shipments.