Under the Whyte notation for the classification of steam locomotives, a 2-10-10-10-10-10-2 has two leading wheels, five sets of ten driving wheels, and two trailing wheels. Because of its length, such a locomotive must be an articulated locomotive. It is not longer than a normal articulated; the fourth and fifth sets of drivers are located under the tender.
Other equivalent classifications are:
- UIC classification: 1-E-E-E-E-E-1 (also known as German classification and Italian classification)
- AAR classification: 1-E-E-E-E-E-1
- French classification: 150+050+050+050+051
- Turkish classification: 56+55+55+55+56
- Swiss classification: 5/6+5/5+5/5+5/5+5/6
- Russian Classification: 1-5-5-5-5-5-1
The equivalent UIC classification is to be refined to (1'E)EEE(E1').
The Baldwin Locomotive Company may have developed a design for a 2-10-10-10-10-10-2 quintuplex; a drawing of this proposal appeared in Trains magazine. It was shown to be the largest and most powerful steam locomotive in the world.