Spiral wound gasket of four specifications for the A, B, C, D Type A basic type, ie without the ring, entirely made of metal and non-metallic band wrapped up for tongue and groove. B type of inner type, suitable for MFM outer surface of C-type, suitable for RF surface, but the pressure is lower than 6.3MPa D-type inside and outside the ring for RF wound pad surface models for the first four digits representatives outer material, the second representative metal band material, material code on behalf of the third and fourth bits represent the inner material 0: 2: 3041: special asbestos paper 0: No 1: Low carbon steel 3: 3162 : Flexible graphite 1: Low carbon steel 2: 304 4: 316L 3: F4 2: 304 4: Non-asbestos paper specially made 3: 316 4: 316L for example gaskets for the 0220 model, is the A-type pad, without the ring, metal band 304, non-metallic graphite 0211 is a B-type pad with inner metal band 301, non-metallic flexible graphite tape is often said metal or metal graphite spiral wound gasket asbestos spiral wound gasket,