Parker hydraulic couplings are engineered to meet a wide range of application needs, with specialized designs organized by category in this catalog for easy selection. Each section highlights the construction and functionality of a specific coupling type. Parker hydraulic couplings are generally classified as either Double Shut-Off or Straight-Thru based on their internal valving. Double Shut-Off couplings are ideal for applications where minimizing fluid loss is critical; both the body and nipple feature automatic shutoff valves that open when connected and close upon disconnection. In contrast, Straight-Thru couplings are designed for maximum flow efficiency, featuring a smooth, valve-free bore that delivers the lowest pressure drop and allows for easy cleaning. However, fluid flow must be shut off before disconnection to avoid spillage. With reliable performance and application-specific functionality, Parker hydraulic couplings offer superior connection solutions for demanding hydraulic systems.