Not much information out there on these, but ordered it anyway. TLD; it's great. This is for a SIG556, the one with the huge plastic handguard with the plastic rails, which my normal sized hands had difficulty negotiating. Yes, this fits. As you cannot see from the pictures or description, it is two piece, and upper and a lower, with the same type of L-shaped brackets to hold it together. It uses a captive lower attachment point, unlike the original, which was a little hook (not a hole, which this on has, held on by the front pivot pin), which is more precisely made and thus requires a little bit of jiggling to get lined up (very tight fit, but use an allen key or punch to gently align it and you will be rewarded). It's not free-floated, but probably not an issue on a rifle with a huge gas system above the barrel. Speaking of which, the gas tube is easily removed with the handguard in place, and goes right back in, too. That's an improvement over the stock plastic thing. Minimal to no wiggle once it's installed. The original plastic one weighed 407 grams on my digital scale, the B&T is 576. If you remove the little metal device on the right to hold the folding stock open (mine had the AR buffer tube mount and did not fold, but now goes right with a Lage stock), you can save 6.5 grams! It screws on with two little hex-heads. Alas, there is no MLOK option, but pretty unlikely to see anyone make something current for a rifle that isn't available any more and didn't really set the world on fire when it was. The bad, besides a non-trivial amount of additional weight that slightly worsens the nose-heavy bias of this rifle? Not much. It is well machined, comes with a discreet but sexy little B&T logo, seems to be durably finished. My only real gripe is the little holes in the rail fore and aft that look like they might be sling mounts, but are not. Just little holes, unthreaded. Hope this helps. The length is perfect for the SIG556, and I suspect it's the same for the classic. Overall, quite pleased, would buy again.