Indicator contact points come in a variety of types and vary based on three main factors. Those factors include shape, material, and extension. The shape of the contact point on an indicator refers to the actual shape of the part that makes contact with the object you are measuring. Depending on the surface structure of the object, such as whether it is concave or complex, grooved, or contains bores or holes, you can vary the shape of the contact point. Another way in which indicator contact points vary by type is by the material they are made of. The most commonly used materials for contact points include carbide, ruby, plastic, and steel. You will want to know the kinds of materials you are measuring to determine the best contact point material. Finally, the type of contact point you have for an indictor can vary by whether or not you have an extension. Depending on the parts you are measuring, having an extension can prove very valuable for improving accuracy.