This is a tool to sniffer WiFi packets over the air which is alternative to expensive Airpcap Windows based WiFi packet sniffing tool. Search Airpcap WiFi sniffer and you'll find how expensive it is when the same task can be done with this tool at a fraction of cost. 

This tool consists of bootable Linux usb flash drive and wifi adapter that supports monitoring mode. You boot your PC from usb flash drive and then capture wifi packets with wifi adapter using built-in tools in bootable usb drive(Kali linux). Since you're booting from USB flash drive, it won't touch your local hard disk at all. So simply you can remove USB flash drive once you're done, reboot, then you're back to your original OS.

Detailed steps about how-to document will be provided upon purchase.(Ebay doesn't allow external link when listing)
Please note that you need PC or laptop with 64bit that supports boot option from usb device.(Most laptops and desktops do but you can check in BIOS mode when PC or laptop boots up)

Bootable Kali linux(17.02 latest 64bit) USB flash drive can be used for other purposes. Kali linux is distribution specifically designed for vulnerability and penetration testing in network and servers and you can have a lot of funs and learn by just playing with it.

I've used this tool many times to troubleshoot wifi problems in my professional career when others purchased Airpcap for a few hundreds $. If you're looking for wifi sniffing tool alternative to Airpcap and have a little bit of experience in Linux, or willing to learn linux a bit, this is right tool for you. 

This sell includes technical support until you get this tool up and running and it is always welcome to return if it doesn't work for you.(return shipping cost on me)