The Pemko STC-series automatic door bottoms are the latest design for high quality performance in acoustic control and sound attenuation. The newly designed spring assembly increases the pressure applied on the drop bar across the entire length of the automatic door bottom, maximizing seal performance. When installed, the high quality, multi-finned seal of the Pemko STC- series automatic door bottoms conforms to slight irregularities in thresholds, sills, and most flooring materials. The seal not only provides superior acoustic performance, but also seals the opening against wind and debris to improve its overall energy efficiency. The expertly designed Pemko STC411 full-mortise automatic door bottom uses the existing 411 door bottom casing enabling installation into the same mortise. This makes retrofit or new installations easy for installers who are already familiar with existing Pemko automatic door bottoms.