Considering how much these things tend to cost in the shop I thought I had found a bargain, after a few weeks it became apparent that it was too good to be true.
The product does do exactly what it says, the problem I've encountered is that the coating on the flexi part of the female connector has already suffered "wear and tear", it's still working fine though I can see exposed copper cable and a coated red wire underneath.
It's possible that this was just part of a poor batch and like I said it does work fine.
My suggestion, if you need a cheap extension cable for use in a dry environment you should be fine but don't get it if it is going to be used in a moist or wet environment (i.e. to extend cable from bag/pocket to head when they is a chance of rain or fog). Considering the low voltages used they should be no risk of harm to humans but it could possibly cause a minor shock (such as static shocks do) and may cause harm to the equipment been used.