Automatically controls grease flow. Refillable through standard hydraulic grease fitting. Contains no chemicals or gases. Allows grease level to be checked at a glance. Sturdy one-piece steel base and core. Safety vents prevent overfilling. Handles grease up to NLGI No. 3. For use on gear box housings and bearings, (such as king pins, universal joints, and more), where excessive pressures are not desirable.