These standard 5/16-inch diameter pitot tubes feature hemispherical tips, which are nearly impossible to damage. The tubes are recommended for ducts 10 inches and larger in diameter. They have inscribed inch graduations on both sides to show depth of insertion at a glance, which helps identify the exact center of any duct. The tubes made of stainless steel comply with AMCA & ASHRAE specifications. They are suitable for use in temperatures up to 1500F and provide accurate readings when its tip is directed within 15 of air flow. The tubes come in seven sizes, ranging from 8 to 60 inches long.