This is a Rectify Series drop-in speaker system for Athearn RTR GP40X locomotives. 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.
 
The speaker comes fully assembled and tested.
 
Overall dimensions are 15mmH x 17mmW x 50mmL