The Argo Hytos ST21A-B2 Needle Restrictor valve hydraulic directional cartridge is a component used in hydraulic systems to regulate the flow of hydraulic fluid. Installed as a screw-in cartridge for a C-10-2 Cavity, this valve restricts flow in both directions, providing precise control over the fluid movement. It's particularly useful for fine-tuning an uncompensated system or serving as a shut-off valve when needed. With hardened precision parts and fine low-torque adjustment capabilities, it ensures accurate flow control with minimal effort. The valve's linear adjustment and positive seat overlap further enhance its performance, allowing for reliable operation even under high pressure conditions. Additionally, its zinc-coated construction provides durability and protection against corrosion.