Air bottle Pipes implementation of the standard is GB18248-2000, wall thickness is 3-55mm. Main material:34CrMo4,30CrMo,34Mn2V,35CrMo,37Mn,16Mn.Diameter: Φ50-325mm Wall thickness: 3-55mm Outside diameter deviation: ± 0.75% Wall thickness difference: -10% - + 12.5% Inner and outer diameter Roundness: 80% of the outside diameter tolerance End face inclination: ≤ 2mm Straightness: 1mm / 1m Surface quality: no cracks, folding, rolling off, from the layer and stalk.