Dboys Sight alignment?

so I am thinking about purchasing this rear flip-up sight.
http://weaponblender.com/index.php?productID=1812
My m4 is a standard m4 with fixed front sight (can't be flipped down)
Will this sight be the same high as my front sight? Will they be lined up with each other?
or will this sight be lower?
I am also thinking of getting this sight because it has a built in riser rail which i need for my G&P 3x magnification optic.

That sight is for the DBOY RDW/KAC PDW, not for a regular M4. I think the PDW's sights are more low profile than standard M4 sights.

Just to play it safe, I'd get something like this:
http://weaponblender.com/index.php?productID=748

i need the rail on the dboys sight also. So at the very least i can use it as a riser (a cheap riser)