Clip in hair extension help?

I really want thick human hair extensions, about 20-24 inch.





Ebay has them for really cheap and they look really thick but I heard that they could lie about whether its human hair or not.


Sally's aren't thick enough for me even when I layer them.





also what type of set is ideal for natural looking clips, I'm thinking about getting a 9 piece.





btw. if this helps I have armpit length medium thick hair.Clip in hair extension help?
http://horrorkidz.com/