Objectives: To investigate gain provided by self-fitting over-the-counter (SF-OTC) hearing aids compared to clinical NAL-NL2 targets, differences between various FDA-approved SF-OTC devices, and potential changes in gain over time. Methods: Two experiments were conducted, 1) a cross-sectional comparison of six SF-OTC hearing aids (n = 43) and 2) a longitudinal evaluation of gain within five days of self-fitting and four additional time points (n = 15). Real ear measurements (REMs) were used to measure gain. Results: SF-OTC hearing aid gain corresponded within 10 dB but not 5 dB criteria from NAL-NL2 targets. Differences between NAL-NL2 targets and gain did not differ significantly between devices. There were no significant changes in gain over time for any input level. Conclusion: SF-OTC hearing aids generally provide user-selected gain levels lower than clinical targets, particularly at higher frequencies. The gain remains stable over time, indicating limited user adjustment after initial fitting. OTC manufacturers should consider implementing fitting algorithms that allow for gradual user acclimatization.