Does anybody have any experience with these?

http://www.gggaz.com/products/ar15ufir.php

Looks like what I'm looking for--I only want to mount a Surefire M900 with vertical grip. Are these solid??
Thanks

Well, I bought one, but I'm not using it conjunction with a grip.  I have a Sure Fire M962SU06 on it, mounted as far back as I can go to get it is as far away from the muzzle.

The problem that I had wiht my UFIR is that the 1st and 3rd holes will NOT align perfectly in the center of the handguard holes.  So when you put the screws through the handguaurds they WILL hit the edges of the handguard vent holes.  ONLY the middle hole on the UFIR will be perfectly aligned with the handguard vent hole.

Does it work?  YES.  Does it suck that it costs so much and the holes aren't perfectly aligned?  YES.  But, seriously, it works pretty good for what I'm using it for.  We'll see how good it is when I go to a tactical carbine class.

As for your application, using a the M900, it'll only be as solid as your handguards.  If you really want a SOLID mount you need to invest in a RAS II or ARMS SIR.

If this is just a range gun the UFIR mount will probably be cool.  But if this is a duty weapon I'd probably spring for a rail system instead.

You may also want to look at Advacnced Armament Corporation web site.  They are offerin a similar mount for HALF the price.

Oh by the way, GGG told me that they were looking into fixing the problem that I encountered.  Heck, for close to $50 they'd better!

I have 2 UFIR's. They work great. I had the same alignment problem on my Colt M4 handguard but not on my std set of handguards. Talking with some other guys they said it is an issue with the M4 handguards. I took a round file and remove a little material from the holes. Fits tight and is very sturdy.

One last thing.  GGG states that you need to mount the UFIR toward the front of the handguard. I don't quite remember exactly what he told me, but I have my UFIR attached to the HG beginning at the second hole of the HG.  He stated that this is important because that's how it was designed or something to that effect.  His words,not mine.

At any rate, I hope this helps.