http://www.hobbyking.com/hobbyking/store/uh_viewItem.asp?idProduct=10592&Product_Name=CR23L_Counter_Rotating_BL_System1100kv_

and also

http://www.hobbyking.com/hobbyking/store/uh_viewItem.asp?idProduct=10591&Product_Name=CR23M_Counter_Rotating_BL_System1550kv_

When you try to make a model like this one. Do a bit of google research on 'Counter /Contra Rotating Props' and you will know why they are used.

Cheers!

VC

'Counter /Contra Rotating Props'
First time seeing/noticing in a plane, normally used in marine applications.

I believe you can use a product like this :

http://www.dionysusdesign.com/product_info.php/cPath/50/products_id/185

and make a coaxial stabilized heli (like the Lama) with the above HK product (along with 2 ESCs and a gyro).  When the all-in-one receiver boards of such helis burn out, people go this route.