The Keymod system is a relatively new alternative rail attachment standard that allows for slimmer and lighter rails than the picatinny system. Strike Industries has just announced their new Keymod rail system for the AK. I believe that the TRAX-1 and TRAX-2 are the first Keymod rails for the AK platform.
The TRAX-1 replaces the AK handguard and mounts to any AK that has a barrel diameter at the gas block of .580 – .631″ and a barrel diameter at the handguard retainer of .657 – .688″. The TRAX-2 is a rail extension that attaches to the TRAX-1 (the TRAX-1 is required to use the TRAX-2). Each of them cost $89, which strikes me as a bargain (please excuse the bad pun). They both include two keymod picatinny rail and will be available in black, Flat Dark Earth and Urban Grey finishes.
One advantage of their modular nature is that the system can be configured in a number of different ways depending functionality you need or how you want your rifle to look.