Bearing pullers and bearing tools are devices for assembling and disassembling bearings. They are often hand-held and manually-powered devices, but this area also includes mountable and powered devices like bearing heaters used before assembly. Typically, these tools are used in the repair of aerospace components, power-generating turbines, and laser-printer toner assemblies. Precision bearing pullers and tools are used with miniature bearings, mechanical components that have an inside diameter (ID) ranging from the size of a pencil lead to the size of a pencil. Precision bearing pulling tools are also used with miniature motors, fly reels, and other devices that are too expensive to be discarded. Non-precision bearing pullers and tools are used in automotive repair shops to fix wheels and in office settings to repair high-volume laser-printer toner assemblies. Typically, a technician uses them to insert or extract an exercised or worm bearing. There are several different types of bearing pullers. Choices include internal pullers, two-arm pullers, and three-arm pullers. Internal bearing pullers and tools are suitable for use with miniature bearings whose IDs range in size from 1/16-in. to 3/4-in. to 2.5-m to 11-mm. These bearing pullers and tools are designed for use with blind holes that are reamed, drilled, or milled to a specific depth but not completely drilled-through. They are also suitable for applications in which a puller cannot be inserted underneath the bearing. Two-armed bearing pullers and tools feature two adjustable arms. Three-armed bearing pullers may be equipped with a safety valve and hydraulic components. Like two arm pullers, they are often used in automotive applications. Bearing pullers and bearing tools are usually made from hardened tool steel or other metals and alloys with high tensile strength. Tool steels are wear-resistant, ferrous alloys that have high levels of elements such as chromium, molybdenum, tungsten, and vanadium. Tool steel alloys are fabricated in their hardened form, and are machined or ground to achieve the tolerances required for tooling applications. Some bearing pullers and bearing tools have knurled handles or other ergonomic features. Others are sold in sets for use with a variety of bearing sizes. For example, a set of five bearing tools may include hand tools that are defined by size. Small bearing puller sets and large bearing puller sets are also available.