Material: The inflatable Boston valve is made of high-quality ABS material, is strong and durable, corrosion-resistant, and does not easily leak air. Size: The bottom diameter of the threaded part is 22 mm (outer) / 20 mm (inner). The specific size of the Boston valve is shown in the second picture. Please check the size before purchasing to make sure your valve plug fits this plug. Application: Ideal for the standard Boston valve replacement kit and most inflatable canoe mattresses, kayaks, swimming pools, boats, etc. The valve is a one-way inflation valve, ideal for quick inflation. The design of the air valve cap is sealed to ensure leak-proof inflation.