These are Rectify Series drop-in speaker systems for Bowser Executive Line U25B locomotives. The speaker uses the factory mounting screws and no modifications are needed to replace the factory speaker.
THREE VERSIONS AVAILABLE
The BOWS-U25E is for the "early-run" models (that were probably never available with sound). The speaker mounts to the large posts holding the rear headlight (which will be removed). These should also work with similar looking Stewart models.
The BOWS-U25M is for the "mid-run" models (most of which had an 8pin PCB). This version uses the BOWS-UNI2 speaker which screws into the four holes using a standard 16x35mm speaker size.
The BOWS-U25L is for the current-run models that have a speaker mounted with only two screws behind the decoder/PCB.
Depending on your decoder installation, a UFIT-Micro can often be placed behind the cab for a dual-speaker configuration. You'll need to measure space for this and select the speaker that best fits: https://www.scalesoundsystems.com/product-page/universal-micro-range
You may need a 2-pin wiring harness to connect the speaker to the PCB. Bowser has used a few different sizes of these over the years. You can choose what size of harness you need based on how your circuit board looks. E-mail me a photo of your connector if in doubt. You can find these in the PARTS section: https://www.scalesoundsystems.com/parts
The speakers come fully assembled and tested.
Dimensions
BOWS-U25E: 15mmH x 18mmW x 36mmL
BOWS-UNI2: 12.5mmH x 16mmW x 35mmL
BOWS-U25L: 17mmH x 18mmW x 35mmL
VIDEO: https://youtu.be/XtS_VIhB6FY