Protective Sleeve

It provides a protective effect for the spline pair during telescopic extension, preventing the ingress of dust and other contaminants. 

Grease Nipple Hole: Grease can be injected into the spline pair through this hole during its extension to achieve lubrication. Its small head end is welded to the shaft yoke; the large head end is embedded with rubber to prevent lubricating oil from leaking out.