Two piece Brown. Automatic Foundation Vents take the worry out of remembering to open and close vents as the weather changes. The vent has a bi-metal coil to open and close automatically without electricity. When the temperature reaches 70F the vent is fully opened to provide fresh air, and fully closes at approximately 40F to conserve energy and protect pipes.  These vents are easily installed using screws, or screw anchors and retaining clips. Both are included with the vents. No mortar is required for installation.  Series 6  Series 5 with oversize frame  Temp Vent Automatic Foundation Vents feature: A heavy duty coil for dependable operation, 8x16 to fit into a standard block opening, A net free area of 50 square inches, The back of the vent is removable for easy cleaning and maintenance