I just got an Aimpoint PRO a while back and my rifle (Colt 6920) has the A2 front sight which provides an absolute cowitness. When I installed the Aimpoint though, I had to toss the carry handle.

I really like the look of the rifle now, but I need a flip up rear BUIS.

Suggestions?

Youll get all the suggests from the BUIS catelog.

I use Wilson Combat Rear flipups, it has elevation and windage adjustments.

This is basically my SHTF gun but I don't need a top of the line rear BUIS either. I'll probably get it roughly zeroed and not use it much after.

Get a Matech off the EE.  Same one used by the military.  $50 max will get you a nice one.  Since you won't be deploying it much, no worries about wearing the locking mechanism out.  The elevation can be quickly adjusted for various distances assuming you have zeroed it correctly.

I have Matechs on all but one of my too many AR15's.  Like the Aimpoint, and other high dollar red dot sights it is GI issue.   Non sure why so many folks don't like them

Need something NIB my completely gun-illiterate mother in law can buy for me online with ease. EE doesn't qualify for that.

Sorry forgot to mention this in the OP.

If you are not going to use the rear folded backup for anything other than true back up and at close range, you don't meed elevation adjustment.  You do need absolute dependability.  For me that means that in that emergency when the backup is all you have and it must be deployed, you don't want to run the risk of it being damaged if struck while in the up position.   Only a few sights will deflect under those conditions.  Most lock upright and will bend or break if struck hard.  

One of the few that will deflect and transfer the energy away from the sight and back down to the rifle upper, is the simple, Magpul MBUS, either the polymer or the MBUS Pro made of metal. Both will deflect.  These are incredibly durable sights and are virtually indestructible.

If you need a rear sight that both deflects on impact and has elevation, then get the KAC adjustable.  It is expensive, but combines both attributes.

For me the polymer Magpul at about $55 is exactly what I need.  Nothing more, nothing less, and widely available.

This describes my needs pretty well. I'm likely to zero the BUIS at 25 yards, fold it down, and not bother with it again. Like you said, it's only going to be deployed in an emergency situation where the Aimpoint goes down.

I suppose, I might occasionally play with it at the range, but it's intended purpose is like you described. A true SHTF, up close and personal backup sight.

Hell, I'm only zeroing my Aimpoint at 25 or 50 yards... haven't really decided yet.

Mbus or mbus pro is what you want than.

Aside from the material differences are they the same?

The pros have a much lower profile is the biggest difference. Can't really think of any other real advantage's to them.

Been very happy with Troy.

I'm a BIG fan of MBUS Pros. I don't think there's a lower profile sight out there...it's also as wide as the top of the upper do it doesn't interfere with using the charging handle...you'll forget it's there.

I run these:

GG&G Spring Actuated BUIS

No he di-ent.                        

I still think the Hahn BUIS is the best thing out there, but they can be tough to find.  Barring that, MBUS Pro.

Get on the EE... find a KAC 300m  or a KAC Micro 300m

I've had those before, they are rock solid.