well they are DAO, and if you want the first polymer pistol ever made, then you are looking at it.
To be honest, if I was going to buy one, I would probably buy a select fire one. As much as I love HK, this is one that I just don't care for. But I will say this, I have never playing with this model I am sure that if I did and I enjoyed it then I will admit it, but I just don't see it happening.
they were designed at weapons for tankers, the real ones have a stock that doubled as a holster, it also had a selector on it to switch from single to 3 rd burst IIRC