Material: The air valve cap is made of high-quality, high-density plastic, ensuring sturdiness, corrosion resistance, and durability. Quick Inflation & Deflation: The air valve cap fits into a 20 mm (0.78 inch) hole and is compatible with Boston valves for faster inflation and deflation. Rubbber Pad: The bottom of the air plug features a rubber gasket that helps prevent leaks and provides a secure seal. One-Way Inflation Valve: Allows for quick and efficient inflation. Design: Features a well-designed valve cap to help prevent leaks, with a two-way air valve system that makes inflation easier and more efficient. Wide Compatibility: Suitable for most inflatable boats, rafts, rubber dinghies, and other inflatable watercraft. Please measure your valve size before purchasing. Color: Black Material: Plastic Package Contents: 4 x Boston Valve, 4 x Gasket Note: This package includes only the items listed above; other products are not included. Note: Lighting and display differences may cause slight variations in color between the image and the actual item. Measurement may vary by +/- 1-3 cm.