Done the video showing what you get. For the Female connector where the headphones (or whatever you're using it for) plugs in, it takes slight force to push the connector in but is very secure because of this. Build quality is usual Belkin and is excellent.
For sound quality, I cannot notice any difference when using the extension and without using it. It's mainly used for the TV. I have tried it on my smart phone just to see? Works great and can pick up more stations on the FM radio.
I will say, in case this happens to you, that the first time I plugged it into the headphone socket on the TV, the sound quality was atrocious, crackly and jumping from ear to ear. After some playing about I figured it was the headphone socket on the TV, which has never been used for years and full of dust. Used an air duster to blow out the dust and now works as it should.