I'm sorry Inade, but I don't think I can believe you much when the website title is called "Picatiny Rail". by all means, that is NOT RIS.
There's a link on that page saying "Rail Integration System", and that's the RIS.
If you are too lazy to read that, then here you go.
"There are different styles of RIS, depending on how much the operator will be accessorizing the weapon. Basic systems that can be installed on weapons such as the previously mentioned AR-15/M16 are usually small rails with holes machined in them that are screwed onto the existing hand guard
on the rifle and can cost as little as $25 to $40 USD. More advanced systems allow for numerous accessories to be mounted simultaneously and cost an average minimum of $200 USD and up for a decent quality system."
ITS the HANDGUARD part.
If you are just so blockheaded and would absolutely not accept the fact, then here's more proof.
It's called a flat top rail.
Sorry Inade, but I take outrageous offence in people trying to look like a smartass but don't even take the effort to read the website title.
I don't know why you guys are trying to make me look like the bad guy here, I'm just trying to correct you. And then what I get in return is people trying to argue with me like there's no tomorrow.
It's fine by me if you wanna look like a dumbass calling it RIS, but I will tell you right now it's called Flat top Rail.