This is a Rectify Series speaker system for Life-Like Proto 2000 BL2 locomotives. It requires removal of the factory PCB and trimmig the plastic "shelf" a bit shorter. The system drops into the frame slots and secures with a dab of adhesive.
 
The speaker comes fully assembled and tested.
 
Overall dimensions are 28.5mmH x 23mmW x 22mmL
 
VIDEO: https://youtu.be/bQL5bzuxA5A