Gents and gals,
This is just a quick post to let anyone (who finds themselves in the situation I found myself yesterday) know that there is a decent alternative to forking out for the ACS Pro-series custom earplugs, if you already own a pair of sleeves for the Etys.
I was very close to ordering a pair of the ACS PRO earplugs for a fair bit of cash, so that I'd stop suffering 2 days worth of tinnitus every time I went to a gig. I've had a set of ER-20 earplugs for a while but didn't like how much they killed the music, so I risked it a few times. Needless to say it scared the crap out of me last week, after a Boban Markovic gig left my ears ringing for a good 2-3 days.
I was looking around at flat-response attenuating filters that I could fit to my sleeves for the HF5, so I ordered a pair of Alpine MusicSafe Pro earplugs for 18 quid. Good news is that the filters fit the sleeves absolutely perfectly, and the 'least attenuating' ones sound great. I haven't compared them to the pro-grade ACS ones, but for a fifth of the price I'm pretty damn happy with being able to use the sleeves for listening, gigging and sleeping (the last one courtesy of the interchangeable 'most attenuating' filter). For what it's worth, the sound the filters let through is noticeable clearer and flatter than my old ER-20's.
Hopefully this will help someone. Here's a pic with the least-attenuating filters. Very easy to get in and out - perfect fit.