Your cooling system has some miles on it - meaning it has endured some heat cycles. Heat cycles make plastic cooling components weak and brittle, resulting in an inevitable failure if not properly maintained. Avoid taking the head off of one more disposable plastic coolant bleeder screw and step up to ECS' engineered-to-last aluminum upgrade. Anodized for long-lasting good looks, 6061 aluminum offers superior durability over plastic, while remaining highly compatible with your modern cooling system's other aluminum components. Includes o-ring.