Compatible with: Amplivox Amplivox 240, Amplivox Amplivox 270, GSI GSI39, GSI TympStar Pro, GSI GSI18, GSI Pello, GSI GSI 61, GSI AudioStar Pro, GSI Audera, GSI Audera Pro, Interacoustics TITAN Firmware & Software (IMP440), Interacoustics Titan hardware improvements (probe/SB), Interacoustics AT235/AT235h Blackline, Interacoustics AA222 blackline, Interacoustics AT235/AT235h New, Interacoustics AA222 new, Interacoustics AA222 with insert headphones, Interacoustics Affinity 2.0, Interacoustics Equinox 2.0, Interacoustics Callisto, Interacoustics Affinity Compact, Natus-Otometrics Aurical, MedRx Avant ARC Complies to all insert phones. 13.7mm.