@F700 I've tried the SD-2 which appears to have the same fit and nozzle. Seal is great due to the custom-like fit and I was able to get a nice flush fit - despite the short and seemingly not so thin nozzle. And yes, deep insertion is certainly possible. Interestingly, the SD series actually measure -35 db in terms of isolation which is basically Ety level (https://www.innerfidelity.com/images/InEarStageDriver3.pdf)
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I am wondering how to get a good seal with such a short nozzle? Is a deep insertion even possible?