Initially designed for use in 3mm scale, these flexible, skinny boxes are now hugely popular with overseas HO modellers, 4mm narrow gaugers, or anyone else struggling for space between the frames.

The 8.6mm diameter axle gear makes the box ideal for small-wheeled engines with 30:1, 40:1 and 54:1 covering a wide range of possibilties. To make best use of the space inside the loco body, you can turn a flatcan motor through 90 degrees to reduce the overall height, with the articulated final drive carriage arranged forward or rearward-facing.

A D3 DriveStretcher can be added to extend the swinging arc by a further 8mm.