Metal drawing dies, in manufacturing industry, are usually made of cemented carbides or tool steels. Mandrels for tube drawing are often made of similar materials as the die. Occasionally diamond die are employed to form extremely thin wire. As the work transverses the mold it passes through different sections. The die's first section is a bell curved opening. This area does not contact the work, but helps filter lubricant into the mold and allows for adequate entry of the work into the mold without damage from die edges. Next, the forming of the work occurs in the approach section. The approach angles down the cross sectional area, connecting with the next section, the bearing surface. Bearing surface, also known as land, holds the precise geometric cross section for a length of the draw. This acts as a sizing operation, ensuring tight tolerances. The last section is the exit zone, this is a steeply angled section similar to the entry zone. Exit zones are used to protect drawn work from the edges of the die.