Preamble: Read here and here for the back story. In short, the Fostex TE-02n are amazing budget IEMs with highly capable dynamic drivers. However, their stock sound signature is a little uneven in treble and overall a tad thin. This mod addresses both issues, fills in the low range, smoothes out the highs and turns them into some of the best DD IEMs I know at any price point. Why "Final+1"? Well, I already had a "final" mod version at some point. Then found out a slight improvement, so yeah... Thanks: To @shotgunshane, @CEE TEE and several other friends (you know who you are) for serving as guinea pigs and providing critical feedback. To @Untilted for introducing me to 3M micropore tape. And to Fostex, for making this gem of a budget IEM in the first place. Speaking of which, looks like the 02n are sadly being discontinued... so grab a pair while they last! Disclaimer: This mod is NOT reversible and will void your warranty, so check your IEMs for any defects before you start modding. Also, this mod requires steady hands and good eyesight. I strongly recommend using a magnifier lamp. Prerequisites (stuff you need to perform the mod): 1mm Phillips and flathead mini screwdrivers (or something else to drill a 1mm wide hole in plastic) 3M micropore tape (widely available, e.g. from ebay or Amazon) A medium sized needle A 40 gauge felting needle (get it from here, or from your local art supply store) The twist tie that comes with the Fostex 02n (don't throw it away!) A razor knife Step-by-step Instruction: 1. Remove the metal front filter. Just stick the needle through one of the holes and lift the plate off: 2. Underneath you'll see a plastic cross-bar: 3. Use the flathead screwdriver to lever it out: 4. A few millimeters down inside the nozzle, you'll see the diffuser membrane that sits in front of the driver. The next step is quite tricky, since you need to pierce a tiny hole through this delicate membrane: 5. Use the razor knife to cut a small piece of insulation off the twist tie. Trim its edges and slide it 0.5mm onto the felting needle. This distance is crucial, since it determines the modded IEM's bass quality! You can check the distance against the diameter of the twist tie wire, which is also about 0.5mm: 6. This is the most delicate and important part of the mod. You need to puncture the diffuser membrane only once and close to the edge. Direct the felting needle slowly along the inside of the nozzle. Don't use force, because the membrane is very thin. Retract the needle as soon as you feel a slight resistance. A perfect puncture should look like this: 7. The rest of the mod is pretty much a breeze. Cut a small piece of micropore tape and place it over the nozzle: 8. Wrap it around the nozzle. The tape is sticky and can be easily fixed in place. 9. Put the tip on and use the needle to puncture the tape four times near the edge. Work only shallowly to prevent damage of the diffuser membrane inside! 10. As a final step, you need to enlarge the tiny rear vent: 11. Use the Phillips screwdriver to enlarge the opening: 12. Finally use the flathead screwdriver to drill about 5mm down: Congrats! If you've successfully made it this far, then you've modded yourself a pair of killer IEMs!