... and air heaters 3, certificate: SGS round four-hole mgo tube:1, with certificate: SGS mainly used as insulation material for ... Φ25x7x50mmΦ26x7x50mm Φ 28x8x50mm3,the mininum OD:1.2mm4,material:99%,99.4%,99.9%MgO power5,apperance:white color,smooth,holes distribute uniformly High temperature ceramic tube