9-round mag from SSS.
Other than that, the FCM uses the same OE mags as other DBM model 10s with no OE extended mags for that model. Alternately, you could get one of the kits to use AICS mags, or have it restocked into something like PDCs custom stocks that use AISC or BO mags, but both of those options are pricey to very pricey.
Bookmarks