Fits:   
Polk Audio 10 Ultra Marine Subwoofer MM1040UM 
Designed specifically for use in the marine environment. New polymer woofer cones and butyl rubber surrounds will not break down over time. High temperature 2" copper voice coil withstands rigorous use while maintaining extremely low distortion for bass punch and output. Stainless steel heavy duty input terminals will not corrode or tarnish. Will accommodate speaker wire up to 8 AWG or twisted pairs of 12 AWG.
Power Handling: 700WPeak 350W RMS
Frequency Response: 24Hz - 200Hz
Sensitivity: 91dB
Impedance: 4 Ohms
Resonant Frequency 35 Hz 
Cutout Diameter: 9-1/8"
Mounting Depth (top): 4-5/8" (bottom): 5-3/16"