This is a Rectify Series drop-in speaker system for Walthers Proto GP35 locomotives using the 28mm round speaker encased within two weight halves held together by screws. No modifications are required to replace the factory speaker.
 
The speaker is a press-fit in the stock cavity, firing down through the frame. The loose half of the weight is discarded. If the speaker is loose in the cavity, a little double-sided carpet tape will hold it securely.
 
The speakers come fully assembled and tested.
 
Dimensions are: 17mmH x 15mmW x 28mmDia