This is a Rectify Series drop-in speaker system for the current-production Athearn RTR locomotives that come with dual-cube speakers. More than just a box, the enclosure features Diapasonic Tuning™, which allows the lower frequencies to accurately develop and resonate, clears the midrange of excess resonance and tunes the upper-mid/high response. The speaker uses the factory mounting screws and no modifications are needed to replace the factory speaker.
 
So far these have fit the SD39-2 and SD40-2 and SD40T-2 tunnel motors. As of now, I'm not sure what other locomotives Athearn is using these speakers in. If you have different RTR loco that has a similar looking speaker, it's a good bet this will fit.
 
You can choose to add front-mounted speakers to these in the form of the AHRR-8550-RC1 (SD38-2) or the UFIT-2115-RC1 (SD40-2).
 
The speaker comes fully assembled and tested.
 
Dimension: 15mmH x 18mmW x 43mmL