Your search for custom car speaker box returned the following:

Custom-fit fiberglass enclosure with 12" W3v3-2 subwoofer — fits 2009-up Toyota Corolla

LOW STOCK

• fits in driver side rear corner of trunk
• one 12" W3v3 subwoofer
• power handling: 100-500W RMS

Custom-fit fiberglass enclosure with 10" W3v3 subwoofer Fits 2005-up Toyota Tacoma Access Cab (Graphite)

LOW STOCK

3 people say 

• graphite Stealthbox® enclosure fits inside the factory center console
• one 10" W3v3 subwoofer
• power handling: 100-500W RMS
  

Custom-fit enclosure with 10" W3v3 subwoofer — fits 2007-up BMW X5

LOW STOCK

• black Stealthbox® fits beneath the cargo area floor in the passenger-side corner of the spare tire well
• one 10" W3v3 subwoofer
• power handling: 100-500W RMS

Custom-fit fiberglass enclosure with 10" W1v2 subwoofer Fits 1988-1999 Chevrolet / GMC Extended Cab pickup trucks (1995-1999, Ruby red)

LOW STOCK

1 person says 

• ruby red Stealthbox® enclosure installs underneath the driver side rear bench
• one 10" W1v2 subwoofer
• power handling: 50-300W RMS
  

Custom-fit fiberglass enclosure with 10" W3v3-4 subwoofer Fits 1994-2004 Ford Mustang Coupe

LOW STOCK

• gray Stealthbox® enclosure fits in passenger side rear corner of trunk
• one 10" W3v3 4-ohm subwoofer
• power handling: 100-500W RMS
  

Custom-fit fiberglass enclosure with 10" W3v3 subwoofer Fits 2004-2007 Chevrolet Colorado / GMC Canyon Crew Cab (Very dark pewter)

LOW STOCK

3 people say 

• dark pewter Stealthbox® enclosure fits in front of and beneath the center of the back seat
• one 10" W3v3 subwoofer
• power handling: 100-500W RMS
  

Custom-fit fiberglass enclosure with 10" W1v2 subwoofer Fits 1988-1999 Chevrolet / GMC Extended Cab pickup trucks (1990-1995, Medium beige)

LOW STOCK

1 person says 

• medium beige Stealthbox® enclosure installs underneath the driver side rear bench
• one 10" W1v2 subwoofer
• power handling: 50-300W RMS
  

Includes a pair of 6-3/4" speakers — fits in 1964-66 Ford Mustang coupe

LOW STOCK

1 person says 

• ABS plastic kick panel enclosures with precut speaker openings
• includes a pair of R-652N 6-3/4" speakers
• fits in 1964-66 Ford Mustangs

1988-2000 Chevrolet / GMC Extended Cab Trucks (1988-94, red)

LOW STOCK

• Installs under the passenger's side rear seat
• single 10" Type-1 enclosure
• internal volume: 0.65 cubic feet