size:hexagonal 22mm,25mm,32mm,centre hole 6--8mm,,it has high strength to keep furnace hole open,keep against the fire back from tube and longer life than tranditional tube,in ordinary,it has 3-4 times longer life than tranditional tube.you may check sandco com cn
| this tube can be moved into furnace over 4m deep and highten melting temperature ,increase output and extend furnace life |