Not quite. The RIS (rail interface system) is nearly identical in construction, parts count, and installation as the RAS.
The RIS (rail interface system) came first, and is the system in use by the US Navy. It is secured to the fore-end by only one clamping foot, which clamps on the handguard cap at the front, and only fits certain diameter barrels.
The RAS (rail adapter system) is used by the US Army and Marine Corps. It has two clamping members, one at the barrel nut, and one at the handguard cap, providing a more secure platform for aiming-point critical accessories such as the PAQ-4C IR aimer and similar. It also fits a wider range of barrel diameters.
Both are machined from an aluminum extrusion, and have the same number of rails and cross-slots. There are RIS's and RAS's available for the carbine, however only an RAS exists for the rifle.