The stylus is an important part of the measuring system. During the measurement, the stylus is in direct contact with the part. Straight styli are the most common type used in the metrology industry. Depending on the application, different materials for stems and tips are available. Ruby is the most widely-used material for styli tips. Thanks to its inexpensive price and high quality, it is the standard choice for most applications. It is an extremely hard material, which tends, however, to cause material build-up when combined with certain materials such as aluminium. A stainless steel stem provides high stiffness and is ideal where weight is not critical for the application.