Enables you to make a quick, positive check for lubricant level and internal hub pressure. Auto pressure control feature prevents overfilling and avoids hub seal damage. When the hub is full of grease, the blue visual check ring rests about 1/8" outward from the steel retaining ring. A spring loaded piston behind the visual check ring pushes against the grease which generates pressure inside the hub to keep water out.

 PROP 65 WARNING: This product may contain chemicals known to the State of California to cause cancer and birth defects or other reproductive harm. Wash hands after handling. For more information, visit www.P65Warnings.ca.gov