ObjectiveThe last decade has offered a multitude of instant fit coupling systems to be fitted with behind-the-ear (BTE) hearing aids. The impact of these designs on the reliability of real ear measurements (REMs) has not been reported. The purpose of this study was to obtain REM reliability data for instant fit coupling systems.DesignREM reliability data was obtained for four different instant-fit coupling systems and for standard size 13 tubing and custom earmolds. REMs were performed for all five coupling systems two times and by two examiners.Study sampleTen normal-hearing individuals (20 ears) served as participants.ResultsThe REM test-retest reliability is high for the four instant fit coupling systems as well as for the custom earmolds. The REM inter-examiner reliability is high for three of the four instant fit coupling systems.ConclusionsCarrying out REMs with instant fit coupling systems appears to be fundamentally no different than performing REMs with conventional hearing aids. For either, care should be taken in probe tube placement in terms of insertion depth and maintaining the probe tube placement, and other best practices regarding test environment and test setup should be observed.