[Ira Delphic]

  I tried this today for my SE215's, the foam plugs I had on hand are too small for my canals.  I had an idea while I was messing with them, I took the shure flex tips and turned them inside out.  I cut the smaller rounded side of the ear plug and put a small phillips screwdriver to make the hole.  I then put the inside out flex tips onto the screw driver and worked the foam onto the stem.  This took a few tries to get it on there.  I pushed the foam all the way down and waited for it to expand, then simply flipped the tips back over the right way and voila!   I like that the flex tips are now stiffer due to the soft foam filling and I get better isolation to boot!  I will take and post pictures when I figure out what the kids did with the camera.
 
Edit 2:  I tried this with my sony hybrids this morning, I ripped the first one and will return to this when I acquire a punch, some of the foam needs to be removed out of the middle as it will only stretch so far. 
I found a retractable pen with a sharp enough tip to punch through the foam.  Much better and easier, I move the foam to the pen slide the sony hybrid onto the pen and work the punched foam onto it.  Easy peasy!  I am happy with the result, I am using bits that I had left over so its not uniform.  I will try them out on my next break.
The earplug foam is much stiffer then the ER4 foam and will probably provide better isolation.  I want to do some head to head with some non-moded hybrids.
 
I also found a wayward ER4 foam tip and "de-cored" it.  The whole thing did fit in a large sony hybrid, although it looked like the hybrid was going to burst, so now I am going to cut the foam tip in half and try them in the larges.
 

 
The ER4 decored foam:
 

 
FYI The earplugs I used are the Hearos Ultimate Soft ear plugs, their blue extreme protection ones you can get free samples of from their website are quite a bit bigger.  I will stop by the store on my home and see if I can find a few different sizes to play around with.
 

 
Blue is extreme protection and beige is the ultra soft

 
Updated: Replying to an old thread. This is EXACTLY what I needed! The leather hole punch tool similar to this does the job nicely.

 

[Ira Delphic]

Basically, two types of foam are used in earplugs - urethane and pvc.  A plug marketed as "non-pvc" is likely urethane. 
There is also polyurethane, which is used by Comply. I haven't tested pvc, but it is harder than urethane and likely less suitable for re-purposing as eartips.
 
From Comply:
http://www.complyfoam.com/pages/Technology.html
 
The earplugs that I've been using to make eartips  is Hearos Extreme Protection blue. The NRR is 33 which is the highest rating. The higher the NRR the better the sound isolation. It is described on some sites as  urethane but I think that it is actually polyurethane. Polyurethane is softer than urethane (and may be less toxic). 
 
I'm experimenting with the Hearos. For long and narrow IEM nozzles a nail or screwdriver can be used to make the hole. For short/wider nozzle such as TTPOD-T1 or Soundsoul S-018 it is necessary to punch out an inner core. I'm using a leather hole making tool, but I've read that a solder iron also works. 
 
I'm not an audiophile. My goal is to make a foam eartip that are comfortable and stay in place, with the grill not being obstructed by the foam. I've had great results with the Soundsoul S-018, but anything is better than the stock tips included. Last night I made foam tips for my T1, but when they wear out will make the foam longer for comfort and open up the end. But still good fit and very good sound. Sound isolation is disappointing.
 
Edit: I contacted Hearos. Their earplugs (or 95% of them) are made of acrylic latex , which is synthetic.

 

[kaiteck]

Bought 10 pairs of foam polyurethane for $1. Will see how it works...

 

[doc elvis]

me using these "ohropax-tips"  since ages and it works on most of my iem`s.
except for my (just new bought) shure se 215, where the nozzle ist very thin.
the tip just fit but my right ear-canal is larger than my left one and obviously too large for this solution on a shure iem.
the stock-tips (no matter how big or small) do not work either for me. there is a kind of seal and sound but it´s lost with every movement...
 
any ideas how to thicken the nozzle up?

 

[Ira Delphic]

  me using these "ohropax-tips"  since ages and it works on most of my iem`s.
except for my (just new bought) shure se 215, where the nozzle ist very thin.
the tip just fit but my right ear-canal is larger than my left one and obviously too large for this solution on a shure iem.
the stock-tips (no matter how big or small) do not work either for me. there is a kind of seal and sound but it´s lost with every movement...
 
any ideas how to thicken the nozzle up?

 
Find some narrow silicon or rubber tips, cut off the outside to the core, and place the core on the nozzle, but not all the way to the base so it's longer. I can see why DIY foam for the SE215 is challenging.
 
It would be ideal to find narrow gauge plastic tubing - like aquarium tubing, but not sure where to source this in small quantitiy.