18"w X 18"h Aluminum Exterior Gable Louver Vent for Walls & Crawlspace - Weather-Resistant Air Grille with Screen Mesh - Black [Outer Dimensions 19.75"w x 19.75"h] 18" Round Duct Pipe this thermostat guard is compatible

this thermostat guard is compatible with most standard thermostat models

Elevate comfort while saving on bills with HVAC Premium's Aluminum Adjustable Return Grill

+ Product Details Size – 20" x 26 or 26" x 20" is the size for the duct opening measurement only

+ Product Details Size - 6"w X 30"h X 2"d (for duct opening measurement only)

Actual Filter Size – 33 3/4"w x 29 3/4" x 1"

18"w X 18"h Aluminum Exterior Gable Louver Vent for Walls & Crawlspace - Weather-Resistant Air Grille with Screen Mesh - Black [Outer Dimensions 19.75"w x 19.75"h] 18" Round Duct Pipe this thermostat guard is compatible+ Product Details Size 18"w X 18"h X 2"d (for duct opening measurement only); actual front end outer dimensions are 19. 75" Width X 19. 75" Height Weather and Pest Proof These louvers are especially designed to prevent water from entering your home, and with a built in back 1 2" mesh they also protect you from annoying rodents like mice, rats, birds, and squirrels High Quality Aluminum The premium durable aluminum will never rust and it will never