For applications requiring sound resistance from STC 56–66, Whisper Core(+) complete door and frame solution meets or exceeds such third-party testing standards as ASTM E90, E1332 and E413; carries 46 OITC rating; and complies with HMMA 865 and SDI 128 specifications. System consists of 2 flush single swinging hollow metal doors within single frame forming communicating opening. Cam lift hinges, flat saddle thresholds, and adjustable door bottoms ensure doors seal completely.