Camera SLR Lenses

Purchased this because the focus motor noise is pretty loud using my Nikon D5100's built in mic, I just wanted something that would reduce the amount of lens noise recorded. Does exactly what I wanted and they sell for around on eBay. In quiet settings it has a very noticeable hiss, so I use the built in mic and set focus to manual. Anywhere with background noise I dont hear the hiss. I'd love a Rode Stereo Video Mic, but I really don't need that kind of quality.