They aren't. The SL-8 was intentionally designed to use a single-row feed 10-shot capacity magazine, due to the *Assault Weapons Ban* Accordingly, there've been conversions for pre-ban M16 magazines or for those fose pre-ban synthetic magazines for the Steyr AUG.
But the modular character of the rifle should make it possible to do all sorts of interesting things with the SL-8 once the AWB sunsets in 22 weeks.
I'm still hoping against hope that the major manufacturers have a whole Santa's sleigh full of goodies to offer once the Ban sunsets. I think they're wisely keeping such things close-hold now, though, to keep them from being used by the Antis as a backdrop for speeches.
I can just imagine DiFi and Scummer standing in front of a poster of some new AR-Asskicker25 or something saying, "Look at what'll be on our streets, slaughtering every baby in sight with automatic, high-powered bullets if this vital, commonsense legislation expires..."