They are made of aluminum and externally powder coated. They insulate PTFE and O-rings on the sealing plugs and connectors. Here you will find the different models and their specifications.
4 Channel Portable Stereo Headphone Amplifier - Professional Multichannel Mini Headphone Splitter Amplifier with Balanced 4 ¼ ”TRS Headphone Output Jack and 1/4" TRS Audio Input for Sound Mixer - Pyle PHA40 BLACK
