This is a Rectify Series drop-in speaker system for Bowser C-628/630/636 & M360/636 locomotives. The speaker uses carpet-tape or a touch of adhesive to mount and no modifications are needed to replace the factory speaker.
You can choose to add a front-mounted speaker for better horn/bell localization using the UFIT-2120-RC1, which sits on the shelf behind the cab.
The speaker comes fully assembled and tested.
Dimensions are: 11mmH x 17mmW x 47mmL