Not very good. - Guntec USA Ultra Slimline Octagonal 5 Sided Keymod Free Floating Handguard w/Monolithic Top Rail

Pro's: Lightweight. Inexpensive. Made in the USA. Timing shims are provided (could be a con).

Con's: Supplied wrench is worse than worthless. Their black color is more of a lighter bluish gray. Very little room for gas block. Wrench flats on barrel nut are too narrow for most crows foot wrenches.

I can't really recommend this handguard unless cheap and light are your overriding criteria. I wasn't particularly impressed with the fit and finish when I pulled it out of the bag.

When mounting, I found the supplied wrench to be worse than worthless. First, it was too big for the barrel nut. If you applied any pressure it would slip off the flats and scar the nut. The wrench has 3/8" and 1/2" torque wrench holes. But the 3/8" is too close to the wrench gap. So the head of your torque wrench won't let you place the wrench over the nut. In addition to the wrench being designed wrong, the metal is far too thin and it came in the package rusty.

Since the wrench was worthless, I tried all of my Crows Foot wrenches and none were thin enough for the wrench flat gap. So forget about checking torque. You'll have to rely on a crescent wrench and your internal torque meter for a guesstimate. Timing was as far off as possible. So I had to use all 5 shims to time properly. I'm not a big fan of shims. I have no proof, but I think they allow movement and negatively affect accuracy.

The handguard has very little room for the gas block. You'll have to use the smallest block you can find. It was an interference fit with the bottom of a Yankee Hill Machine 9384. So I dug around and found an old Parallax Tactical lightweight XPXTLP750LW. It's very low profile and the set screws on the bottom still just barely cleared the handguard.

I guess I'll find out if it holds up over time.

Caveat emptor. You get what you pay for.