Yes, ER20 are cheap and disposable, but there is no reason why they can't be cleaned and maintained from time to time as any other piece of gear.
[1] First, flip the largest of the three flanges upward.
[2] Hold the larger part of the out clear plastic cap with two fingers (blue). Feel the inner tube under the silicone eartips and hold it with two of you finger tips (red). Beware that your long finger nail can damage the silicone so be careful here.
[3] Using your figure tips (red), carefully rock the inner tube front and back slightly in a circular path and pull outward occasionally. For those who played w/ tubes before, it is a very similar process like pulling out tubes. Keep repeating until the inner tube is pulled out from the clear plastic cap.
[4] You can pull the tri-flanges out from the inner tube.
[5] The cap and the tri-flanges can be washed with water (or a bit of mild soap), but the filter on the inner tube is glued on with double side tape so washing is not recommended. If the tri-flanges has became yellowy and oily, now is the time to replace it. Untrimmed tri-flanges from Etymotic or Shure will both do the job. Remember, the stem of the tri-flanges must never be trimmed or it will not be long enough to fit the inner tube.
Enjoy!

[1] First, flip the largest of the three flanges upward.

[2] Hold the larger part of the out clear plastic cap with two fingers (blue). Feel the inner tube under the silicone eartips and hold it with two of you finger tips (red). Beware that your long finger nail can damage the silicone so be careful here.

[3] Using your figure tips (red), carefully rock the inner tube front and back slightly in a circular path and pull outward occasionally. For those who played w/ tubes before, it is a very similar process like pulling out tubes. Keep repeating until the inner tube is pulled out from the clear plastic cap.

[4] You can pull the tri-flanges out from the inner tube.

[5] The cap and the tri-flanges can be washed with water (or a bit of mild soap), but the filter on the inner tube is glued on with double side tape so washing is not recommended. If the tri-flanges has became yellowy and oily, now is the time to replace it. Untrimmed tri-flanges from Etymotic or Shure will both do the job. Remember, the stem of the tri-flanges must never be trimmed or it will not be long enough to fit the inner tube.

Enjoy!
