Even if they look the same, Keymod is a bit different to the HKey system from Heckler & Koch! Means for you as customer, that if you choose a Keymod handguard, you also need the keymod picatinny adapters to attach things...
Keymod will not fit HKey from HK - and the other way around!
So if you choose a HK HKey system, make sure the additional picatinny adapters are also HKey!
At least both systems are well functional and we can`t say which one is better - they are too close together.
We hope this helps a bit!