IMPORTANT SIZING NOTE - Most plumbing products are measured using BSP thread dimensions which measure 1/4 inch larger than that stated, therefore this 1/4 Inch BSP thread actually measures 1/2 Inch in diameter. If your thread measures 1/4 Inch in diameter then you require the version of this product This listing is for a single 1/4 inch BSP radiator bleed valve. This radiator bleed valve is machined from high quality brass These radiator air vent screws are designed to manually bleed trapped air from a closed system This radiator vent valve has a 5mm square drive, overall length of 17.5mm and a thread length of 10mm, Weight: 0.0440924524 Pounds, Manufacturer: Primaflow