External gear pumps are the most common type of pump for hydraulic power applications. This is because of their simplicity, reliability, and very high power ratings. A typical 10 hp (7 kW) gear pump may fit into a 4 x 4 x 4 inch (100 by 100 by 100 mm) envelope, a fraction of the size of a comparable electric motor. Maximum operating pressures are between 1000 and 4000 lbf/in² (7 and 28 MPa).

Many commercial models are designed to operate as either a motor or pump. Some designs add load sensing modifications.