I use King Arms in my KWA, so if Jubz12 KWA fit ICS then it stands to reason that King Arms must fit ICS too.
I thought pretty much every brand of M4 mag fit almost all brands of M4, I've heard that only the TM recoil series, G&G, Systema and obviously GBBR mags were meant to cause problems.
Surely if you phone or email the retailers they'll be able to let you know? Try ringing WolfArmouries, they certainly stock all the necessary things to check it out for you.
As for buying them, try Airsoftsupplydrop, they accept returns so just buy away and if they don't fit, send them back.
Simple pimple.