There are many fake headphones and earphones on eBay, most often from Chinese sellers, this includes the wonderful 
PX100 from Sennheiser. Check out my review where I compare the FAKE with a GENUINE PX100, both in terms of looks and sound. Then decide which you want!

So... Caveat Emptor! Buyer beware! (Because God knows, eBay & Paypal won't cover you, if you get ripped off. They're too busy laughing all the way to the bank from all the profits they make off of Chinese & other scammers).

High chances of it being a fake are:

* Seller is in China
* Seller is registered in a country other than China, but is really in CHINA
* Seller sells the phones in a plastic bag (not original box)
* Price is significantly lower than sellers that show the original box in their ad
* Seller's record is riddled with feedbacks complaining about FAKE headphones


DIFFERENCES BETWEEN FAKE SENNHEISER PX100 AND REAL:
 

LOOKS:
=====

REAL:

* headband is a duller, matte black
* logo is stamped on a glossy black inset plastic
* earcups click into place when folded out
* "CE" logo on inside of headband (on one side)
* screws are black
* Sennheiser logo on headband is grey, & larger
* Braille markings on outside of headband (indicating channel)
* Length from separator on wire where it forks into a Y to the earcup is 12"
* total cord length is .5" longer
* cord a bit more flexible
* foam pads are more cushiony, better material

FAKE:

* PX100 logo stamped in white direclty on band and upside down!
* Closed, headband is larger and wider
* Cushioning under headband is harder and thinner
* Earcups have a smell of moulded plastic
* R/L etching on headband is larger, deeper etching
* Hinge is larger
* logo is brown, and smaller
* Length from separator on wire where it forks into a Y to the earcup is 15"
* total cord length is 40.5"

Top one is REAL, bottom one is FAKE. REAL has larger logo in grey. FAKE has smaller logo on brown.

REAL is on left, it has PX100 logo on glossy black plastic inset. FAKE is on right, it has PX100 logo in white, directly stamped on headband.

(This one's harder to make out, bad camera!). The top is REAL, bottom is FAKE. REAL has a "CE" logo engraved in the inside of the headband. FAKE has nothing.

SOUND:
=====

The moment I heard the PX100's from the store it was clear that they were different. What was less clear, was whether they were better! It was evident that the sonic picture was smaller with the real Senn's, things were less separated, and more further away (on the fake senn's, bass, mids and highs were more "in view").


REAL Sennheiser PX100 (as compared with FAKE)

---------------------------------------------------------------

* Better, tighter, slightly more comfy fit (probably helps sound quality)
* More refined sound
* "Whiter" tonal quality (even icy white)
* Faster, "zippier" transients (leading edge of notes)
* EVERYTHING is less prominent; vocals, bass, jazz horns...
* Less separation (between instruments, etc)
* Sound is more "in your head"
* Musicality more mentally engaging
* More neutral

FAKE Sennheiser PX100 (as compared with REAL)
---------------------------------------------------------------

* Slightly looser fit
* Reversed left / right channel!
* Bass less well defined but more prominent, as with everything
* Singer sounds more "in the room" than in your head
* Gives less music in some ways (less accurate musical information), but more music in others (ie. has larger soundstage, greater body)
* More tonal coloration across the band
* Musicality more physically engaging
* Lyrics clearer, probably easier to sing to music (because of more up-front & clearer vocals)

DON'T FORGET to vote "helpful" if you found this guide helpful, and if you are in the market for a Chinese unbranded mp4 player to go with your fake Chinese PX100's, check out one of my other Guides. Thanks for reading!