The Swagelok SS-4R3A is a 316 stainless steel high-pressure proportional relief valve designed for over-pressure protection in liquid or gas service. It features 1/4-inch Swagelok tube fitting connections on both the inlet and outlet.

The brown spring for the Swagelok SS-4R3A (R3A series) designates a set pressure range of 2,250 to 3,000 psig (155 to 206 bar). 
It is one of eight interchangeable springs used to customize the relief pressure of this high-pressure valve. 
Technical Specifications