1 week ago, I bought a 6" barrel extender for my HK416. I received it today, exactly 1 week later. Price was $18.50US shipping included. Doesn't get any better than that.
There are a lot of great items on that site, and the fact they don't charge you $40 shipping on a $10 item (like eHobby, Redwolf, etc...) is extra bonus.
That being said, eHobby and others have a much larger selection to choose from, and will carry gear that ebaybanned doesn't. But if it's available from ebaybanned, you'll get it way cheaper than any of the other China / HK retailers just because shipping is free.