Designed for Environmental Test Chambers, E-Plug™ Chamber Port Plugs press fit into access openings to seal against air, humidity and temperature escape, or ambient air entry into testing environment. Standard E-Plugs™ are made from 4 in. thick silicone foam with .125 in. thick closed cell silicone foam skin on one side, while Semi-Custom E-Plugs™ are fabricated from pre-made 4 in. thick silicone foam sheets with skin on one side. Foam remains flexible at temperatures from -67 to +392°F.