12-3 louver is an aluminum louver vent with 3 vanes that adjust to allow air flow. The sizes are an overall size of 12″ wide x 12.25″ high, and the cut-out required is 10.5″ wide x 10.25″ high. Included back screen to be placed on door back to deter dog of extending through louver. The back side requires a min. of 3/4″ clearance to allow pivot arms to clear.