I purchased a boatload of the overseas extentions of various sizes and so far there fine, a good old servo test, plug it in and wiggle the sticks,and move the connector a bit if it works then there OK to use.

on the ones I have the connector is a nice tight fit with no slack, so far, if you notice the servo lead is loose in the connector junk the extension and try a new one.

on the ones I got I paid .01$ the shipping was the cost couple of bucks is all, there fairly well made, there just a wire and a plug not alot too them.