A21F、A21H-C type used in ,working temperature≤200℃ air , ammonia, liquefied petroleum gas equipments or pipelines
A21W-P、R type used in ,working temperature≤200℃, corrosive gas or liquid equipments or pipelines, as over-pressure protection device.
KA21Y type used in ,working temperature≤100℃, liquefied petroleum gas, etc.