Specification :

Resiliency and strength make spiral wound gaskets a good choice for a variety of applications and environmental conditions.
They are made from winding a thin strip of metal wire, with soft fillers added to create an effective seal, and often have an outside centering ring, with an inner ring to offer additional radial strength.
Spiral wound gaskets have markings that indicate the manufacturer, the winding and filler materials, the pipe size (nominal), and the materials that the inner and outer rings are made from.
The markings conform to ASME B16.20.