CRL No-Draft Mail Slots are designed to keep out the weather as well as dust and dirt. The CRL No-Draft Mail Slot has two door flaps, both spring-loaded and weather-stripped, as well as an internal brush strip for greater insulation and privacy. Both the external and internal flaps open to 135 degrees for easy access. Both have durable nylon torsion rods instead of springs to keep both flaps tightly shut. Made from high impact ABS plastic and anodized aluminum, CRL No-Draft Mail Slots will not rust or tarnish over time. Easy-to-install by simply running a bead of CRL Cat. No. RTV408C Clear Silicone on both the interior and exterior sleeves and attaching each side to the glass around the 10-1/4" (260 mm) wide x 1-7/8" (48 mm) high cut-out. Intended for horizontal orientation where glass surrounds slots on all four sides.