A note to those with fit problems, I have one of ClieOS' cables with the right-angle connectors as shown in this photo, and it's helped with my fit issues.
With the stock cable the bend of the connectors is right up against my earlobe and I still can't get a good seal with the comfortable small triflanges. The long-stem triflanges (not part of the standard fit kit, I think, but available from Etymotic separately) mostly solve that problem, but it's still not quiiite as solid as I'd like on one side.
(This is with ER4-SR. The ER-4S driver/connector combination was long enough that I didn't have this problem.)
The right-angle connectors ClieOS uses give a few (2-3?) mm of extra potential insertion depth compared to those on the standard cable. For me that extra depth allows a great fit and seal with the stock grey triflanges.