They look a little strange, but are incredibly comfortable. I do not feel anything inside my ear canal, and on the outside, only feel a slight drag from the weight of the IEMs themselves. Currently, I'm using JVC FXD80 IEMs, and the custom mold helps accentuate the bass, open up the soundstage, while providing greater isolation than before. This mold is easy to do, and only took me around 30 minutes.
First things first. I purchased the Radians Custom Molded Earplug for the job. From amazon, they were $9 with shipping when I bought them. Easily worth the price, in my opinion.
Opening the package, you see this. (Being an idiot, I forgot to take pictures, so I borrowed these from makezine.com)
This nice gooey, oily mess. But it works nicely. Read the instructions first! And a fair warning: there have been reports of the earplugs not curing at all, so you are left with gooey mold in your ear. From what I've read, this stuff expires, so try to get an earlier batch. Mine was made around 1.5 months before I used it. I also pinched off a little to test the curing first. Just in case.
Step 1: Clean out your ears! Anything in there will affect your molds. I used this little wooden gouge to scrape out all the earwax, then used q-tips with isopropyl alcohol to swab everything out. Don't forget the outside of your ears too!
Step 2: Preparation. First, mask off your IEMs with some saran wrap stretched over the driver. This stuff didn't stick to my IEM, but I wanted something to protect the internals from the silicone. So I just placed some saran wrap over the opening. You don't want it all the way down the base, since you want the earplugs to grip the valleys in your IEMs.
Step 3: Now, this stuff hardens in 10 minutes. So make sure you have the following things: a mirror, a bite block, and your prepared IEMs.
Step 4: Separate the putty. The instructions say divide them in half. I was able to use a quarter of the material for each ear- since the earbud takes up space. So I divided the color putty into 4 equal pieces, and the white putty into another 4 equal pieces. Your mileage may vary.
Step 5: Ready? Get a timer. Use thirty seconds to very thoroughly mix the putty together. Use your fingers, massage, squish, and mix well! Make sure to get it well done, or it may not cure at all.
Step 6: Now, place the putty just outside the canal, and massage it into the crevices. You don't want too much over the ear canal, since the IEM will be pushed in there, and you will cut off any extra putty that gets in front of the drivers. Once you have it nice and smooth, push in the IEM. It should look like this:
Sorry for the off-centered picture, it's really hard taking a picture of your ear. But use a mirror to make sure everything's in there correct. When you insert the IEM, try to get it going into the canal as centered as possible. Push it deep- until it becomes uncomfortable.
Just to recap. How I molded it was I placed the putty at the leftmost part of my ear (see above picture.) Then, I massaged the top part into the top fold of my ear, massaged the bottom bits into the bottom of my ear, and took the remainder and spread that over and into my ear canal. You only need a little bit covering your ear canal because whatever is over the canal is wasted when you cut it off to expose the driver. But the little bit covering it is still important because some of it spreads to ensures a seal between the IEM and your ear canal.
Step 7: You want something around 0.5" to 1" wide to use as a bite block. Place that between your teeth. This helps shape your ear canals and ensure a good mold. Now, wait. At around 4 minutes, the cure begins, and you should hear slight popping in your ear. The instructions say to wait until 10 minutes, I waited until 15 just in case. The popping sound doesn't stop, but it was solid and pulled out easily.
There's my plug. The rounded cone to the top left will need to be cut off.
Step 8: Cut off the rounded cone- expose the drivers.
I missed a little with the centering of the earbud, but it doesn't affect the sound. It's just a little weirder looking.
Now, just repeat for the other ear, and you're good to go! Oh, and obviously remove the saran wrap before you use the earbuds.