I've had customs with and without. I can't tell much of a difference. I received the standard ADEL modules that came with the molded set.
Thanks for your honest comments! We agree that some people don't notice a big difference in sound with and without the ADEL. We tend to get more effect of the soundstage as you add more monitors with the ADEL. With more differentiation (the added speakers/drivers), the soundstage opens even further. At least you can feel that your ears are not getting fatigued as with other brands, and protecting your hearing is surely invaluable.
The fit is superb! The ear buds literally sink into my ear, without pushing them in, and they stay put creating great isolation.
I chose different color (gold, silver) logos for each ear bud, for quick reference. However, the colors are too similar on stage/lights. No problem, the ear buds are factory labelled "left" and "right."
Sound quality is high, partly due to the isolation.
I like my Inearz P350 w/ADEL very much. Highly recommend.