H&K is coming up with MR556A1-SD which incorporates SD design from Operatos Suppressor Systems. It also comes with Modular Rail System which looks like Keymod backwards.
You can read more about it in the product sheet in the link
http://blogs.militarytimes.com/gearscout/2014/01/07/heckler-koch-introducing-mr556762a1-sd-with-oss-suppressor-and-new-handguard/
From: Gear Scout