These are drop-in speaker systems for the Scale Trains GTEL 8500 Big Blow Turbines.
 
For both Rivet Counter and Museum A-units, the KATO-P42R-RC1 speaker mounts within the stock speaker housing. Simply remove the grill and stock speaker from the housing, stick the KATO-P42R in the stock housing with mounting-tape and solder the wires. The SSS speaker will yield much fuller and clearer sound with more volume to the hostling engine and horn/bell.
 
TWO B-unit/Turbine speakers are available.
 
The Rivet Counter B-unit speaker can use the SXTH-BLOW-RC1, a half-round speaker that slips into the turbine exhaust casting. The stock speaker should be disconnected but can be left in place. This speaker will fill-out and smooth-out the turbine sound, giving it the deeper "whooshing" sound the prototype had.
 
The Museum B-unit speaker uses the SXTH-BLOM-RC1 and replaces the stock speaker sandwiched between the chassis halves. It is a drop-in replacement using the stock mounting-screws. This speaker will fill-out and smooth-out the turbine sound, giving it the deeper "whooshing" sound the prototype had.
 
The Rivet Counter B-unit can also use the SXTH-BLOM speaker, but the SXTH-BLOW speaker that fits in the turbine part sounds slightly fuller and is a simpler install.
 
The speakers come fully assembled and tested.
 
VIDEOS: https://youtu.be/7n66Lhm_h94