The Oil-Seal Plug 86632916 is designed to seal auxiliary holes in HC25 Hydraulic Rock Drill cylinders, where oil leakage could compromise system pressure. Generic plugs often omit sealing elements, leading to slow leaks that waste oil and reduce efficiency. This OEM plug features a built-in rubber O-ring that creates a reliable seal against cylinder walls. Its threads are precision-machined to ensure a tight fit, preventing loosening from vibration. Constructed from corrosion-resistant steel, it maintains performance until damage or loosening requires replacement.