I have the mach ones. I used them in the emb-145 before my furlough. Worked wonderfully in the RJ. Now I'm using them in the caravan, and they work great. It's just like wearing ear plugs, the sound quality is amazing. They do make custom ear molds, but I've just been using the blue silicone/whatever they are plugs. You do have to grab the top of your ear and cram them in there, but other than that they work great, are light on your head, and you can wear sunglasses all day and not have a problem or a massive headache at the end of the day!
They are quieter than the sennheiser hmec-400 (with sunglasses on, as the seal is broken) with the glasses off, they aren't as quiet. I love mine and would like the custom ear molds, you don't have to use the ear hook if you have the molds. I'm just too cheap and lazy to get them done. I'm hoping that they have a special booth at oshkosh so I can get them in the week i'm there, but i doubt it. Also, they aren't TSO'd, so if your company decides that you have to wear a tso'd headset, these are out. I really enjoy them.