Auvio tips look like gel single flanges, perhaps slightly larger. Unfortunately, cannot have any kind of super deep insertion with such tips or silicones - they get rotated at the 2nd bend and blocked. Sometimes that even happens at the first bend, but usually it's possible to just insert to the reference plane. Comply on the other hand get "squashed" at the 2nd bend and keep securely in place. I don't know of any audiologist in Poland, Warsaw who can make ear canal impressions way past second ear canal bend. If I knew one, I'd have made such very deep ones for SE-5 - all of them put the otoblock right there and thus make impression that go up right to the second bend - just at the reference plane. A long small triple flange can't do it for me either, as the ear canal is curving there - they get very uncomfortable. RE-400 shell is just the right shape to go itself past the 1st bend (well, could be slightly more rounded reducing the minimal discomfort), similarly to Etymotic ER-4S shell, or perhaps VSonic GR01, which I haven't tried yet. The tricky proposition is removing it - have to pull gently by the strain relief.