What plugs do I need ?
Twin Plugs are found in almost all GA aircraft and most Boeing 737s. U/174 (also known as US NATO) is used in most helicopters. LEMO plugs can be found in some GA aircraft and helicopters but are certainly not universal. XLR5 connectors (also known as Airbus connectors) are primarily used in Airbus aircraft and a few Boeing 737s - mainly those of Transavia and Norwegian as well as some military aircraft.
High or low impedance? High impedance headsets are the norm, low impedance headsets are almost exclusively for use in military aircraft.
Headset Plugs - the most common varieties