A normally closed, quick opening valve, the 305A is often referred to as a "Whistle Valve". This valve has been in service for many years on agricultural and industrial applications, for both compresses air and liquid. The valve body is heavy cast brass with internal components of machined brass. The standard valve disc and O-Ring are Buna-N. Teflon and Viton seals are available on most sizes. Springs are stainless steel.