SoundTraxx 40 X 20mm Oval Speaker
 
This is a great speaker for many HO and S-scale locomotives.
 
Dimensions: 40 x 20 x 8mm(D)
Frequency Response: 550Hz - 12kHz
Power: 1 Watt (Nominal) 1.5 Watts (Peak) 
Impedance: 8 Ohms
 
MSRP; $15.95