Pemko 4131CRL36 Semi-Mortise or Surface Mount Automatic Door Bottom with Black Sponge EPDM seal 36" long. This Pemko automatic door bottom consist of an 19/32" x 1-27/32" Clear Anodized aluminum case which surrounds a movable drop bar seal. The drop bar seal is actuated by a plunger which contacts the jamb as the door is closing, forcing the drop bar seal down against the floor or threshold. Especially over Even surfaces the Sponge EPDM provides an excellent seal to keep out draft, dust, moisture, insects, fumes, light, and sound. This door bottom is designed to seal a gap of 1/8" to 3/4" from bottom of the door and can be trimmed as much as 2" in length. Screw holes are slotted for adjustment. For Semi-Mortise surface or flat surface mount installations.