M4 Rear Sight?
 

I'm looking into buying an m4ris and i plan on getting an aimpoint 4x scope with a canteliever mount. I want to build my gun like this...

http://www.airsoftcanada.com/gallery...3_original.jpg

Now for my question,
the one on the bottom has a rear flip up sight, now do i have to buy that, or is that just part of the carrying handle?

You either buy it, or get the Marui carry handle and cut it down your own.
Look at WGC, they have it.

http://www.wgcshop.com/pcart/shopper.php?cat=Sights

You can cut of your carrying handle OR buy one, generally speaking it's cheaper to BUY a carrying handle and cut it. I have one up for sale if you want.