There are two types of titanium frames: pure and alloy. Pure titanium is approximately 99% pure, while titanium alloy (also called “memory titanium” or “bendable titanium”) is made of about 25% other metals (such as nickel and copper). Both types of eyeglasses frames are lightweight and durable, but memory titanium has properties that make it great for flexible eyeglasses because it can be bent into whatever shape is needed. These characteristics are useful for temple arms, because they can be bent in a way that will provide a snug and comfortable fit.