It seems like on some flattop ARs the handguard rails go right on to the rails on the upper. What is that called?

Here are examples of what Im talking about:

Have you seen the LMT Monolithic Rail?

www.lewismachine.net/product.php?p=57&cid=&session=9bcaf10ba92f28448bb3378e7f234eb3

I can't remember who makes the example in picts 1 and 3, but I've seen them.  I think it's actually a free float tube and a rail that attaches to the upper and contacts the free float...they're not one unit.

The middle one is a (enter company, I don't remember) free float 4-rail Monolithic "Look" hand guard.

What do the experts think?  Am I close?

-JBot

Quoted: Have you seen the LMT Monolithic Rail? www.lewismachine.net/product.php?p=57&cid=&session=9bcaf10ba92f28448bb3378e7f234eb3 I can't remember who makes the example in picts 1 and 3, but I've seen them.  I think it's actually a free float tube and a rail that attaches to the upper and contacts the free float...they're not one unit. The middle one is a (enter company, I don't remember) free float 4-rail Monolithic "Look" hand guard. What do the experts think?  Am I close? -JBot

Wow $1,200!? Thats crazy. So its a monolithic rail. Who makes some? I like them.

The first and the last pics are bushmaster carbon 15s. The middle is a S&W M&P-15