Black Cap Large

The ALLSTAR PERFORMANCE Black Cap Large (ALL99366) is a screw-in filler cap engineered for cooling system applications across a wide range of automotive and motorsports equipment. This 3.000-inch outside diameter aluminum cap features black anodized finish for corrosion resistance and durability in high-heat engine compartments, making it an essential replacement component for any vehicle requiring reliable radiator or overflow tank sealing.

The aluminum construction provides excellent thermal stability and won't degrade under sustained coolant temperatures. Black anodized coating protects against oxidation and salt spray corrosion—critical for off-road vehicles, marine engines, and competition cars exposed to harsh environments. The screw-in design ensures a secure, leak-proof fit when properly threaded onto compatible reservoir or radiator necks, preventing pressurized coolant loss during operation. At 0.51 lbs and compact dimensions (5.5 x 1 x 9.05 in), this cap is easy to handle and install without special tools.

This universal-fit cap is ideal for hot rod builders, race teams, restoration shops, and powersports enthusiasts who need OEM-quality replacement cooling system components. Whether replacing a damaged cap on a classic engine rebuild, upgrading aging cooling hardware on a performance vehicle, or stocking spare parts for field repairs, the ALLSTAR PERFORMANCE filler cap delivers the robust construction expected from a manufacturer trusted in high-performance motorsports. Each cap is sold individually, allowing targeted replacement without unnecessary bulk purchases.