This is a Rectify Series drop-in speaker for Athearn Roundhouse EM40 locomotives.  The speaker mounts into the roof of the cab with double-sided mounting tape. The only sound decoders that will fit this model are the LokSound 5 58823 Micro and 58923 Nano decoders with wires. A TCS KA1 can be installed next to the decoder (highly recommended).
 
The speaker comes fully assembled and tested.
 
Dimensions: 7mmH x 30mmW x 17mmL
 
VIDEO: https://youtu.be/tfxxX11bEP4