P990..... DAO
P99....... DA/SA
P99/QA.. partially precocked like a Glock - all models
P99/AS...DA/SA post - 2004 open rail
P99/DAO.DAO post - 2004 open rail
On the QA you can not select DA or SA.... it is same triggerpull every time
on the DA/SA if you want to shoot DAO you need to decock after every shot...