#4 Steel Cap

The #4 Steel Cap by AEROQUIP is a professional-grade hydraulic fitting cap designed to seal and protect AN-sized connection ports in fluid power systems. Engineered for technicians and equipment operators who demand reliable sealing in demanding industrial, mobile, and aerospace applications, this steel cap prevents contamination and fluid loss when connections are temporarily unused or between service intervals. Its compact design and durable construction make it an essential inventory item for maintenance teams and professionals managing complex hydraulic assemblies.

Manufactured from steel with a zinc oxide finish, the #4 Steel Cap delivers corrosion resistance and extended service life in harsh environments. The zinc oxide coating protects against oxidation and provides a secure, low-profile seal that prevents dirt, moisture, and debris from entering critical hydraulic ports. This set includes six caps, offering economy and convenience for stockpiling across multiple equipment locations or fleet maintenance operations. The compact footprint—measuring 2.35 x 1.1 x 3.75 inches and weighing just 0.16 lbs—ensures easy storage and handling without adding burden to tool kits or spare-parts inventories.

Hydraulic system technicians, equipment maintenance crews, and OEM service departments rely on the #4 Steel Cap to maintain port integrity during equipment downtime or component changeovers. Compatible with standard #4 AN (AN4) ports, these caps are commonly used on heavy equipment, aircraft, mobile hydraulics, and stationary industrial systems where fluid purity is non-negotiable. The set of six provides redundancy and cost efficiency, eliminating downtime caused by lost or misplaced caps. Installation requires no tools—simply thread onto matching AN4 ports by hand for secure, immediate protection.