Under the Whyte notation for the classification of steam locomotives by wheel arrangement, the is a Garratt locomotive. The wheel arrangement is effectively two 4-6-0 ten-wheeler locomotives operating back to back, with the boiler and cab suspended between the two swivelling power units. Each power unit has two pairs of leading wheels in a leading bogie, followed by three coupled pairs of driving wheels and no trailing wheels.
A similar wheel arrangement exists for simple articulated locomotives, but is referred to as . On a simple articulated locomotive, only the front engine unit swivels while the rear unit is rigid in relation to the main frame.
This was a rare wheel arrangement for Garratt locomotives, with only seven locomotives built for two South American customers.