Titanium is a metallic element that is characterised by strength, lightness and corrosion resistance. Though it is as strong as steel, it weighs about 55% less.When alloyed with other elements such as iron, aluminium, vanadium and molybdenum it produces strong, lightweight alloys for high-stress applications such as aerospace (jet engines, missiles and spacecraft), and extensively in manufacturing industries. Spectacles frame of the alloy of nickel and titanium (nitinol) when bent, flexed or twisted returns to the original shape because of the memory effect. Because titanium is biocompatible (non-toxic and not rejected by the body) it has many medical uses such as implants. Titanium, used to make this lightweight pair of women's glasses, has the additional advantage that it is hypoallergenic unlike metals to which some people are allergic such as nickel, cobalt and chromium.