Titanium is recognized for its high strength-to-weight ratio it is a strong metal with less weight that is quite malleable (especially in an oxygen-free environment). The relatively high melting point (more than 1,650 °C or 3,000 °F) makes it useful as a refractory metal. Titanium is corrosion resistant in seawater, aqua regia, and chlorine. Titanium grade 1 is the most ductile (lowest tensile strength with an oxygen content of 0.18%), whereas titanium grade 4 is the least ductile (highest tensile strength with an oxygen content of 0.40%). Titanium grade 2 and grade 5 are alloys, each designed for specific properties of ductility, strength, hardness, electrical resistivity, creep resistance, specific corrosion resistance, etc. Ti 6Al-4V is one of the most commonly used titanium alloys used in applications where low density and excellent corrosion resistance are necessary. Titanium round bar is a very popular go-to for a multitude of products, from fasteners to jewelry. The medical field often uses the small-diameter round bar for body implantable fasteners and dental appliances. Larger diameter round bars are used for clutch and flywheels. Titanium stops the heat and does not transfer to the rest of the assembly hence titanium sheet is often used as a heat barrier. Titanium plate and sheet have ballistic properties making it great for driver protection in racing.