that is probably for a SMIC, but you might call them and check. if you go weapon R, go ahead and order new set of couplers too. from what i hear, they are not that great with that kit.
+1 on buying a kit complete. it beats the hell out of buying it all in pieces (as far as the guess work of compatibility). you will end up with a higher quality kit if you build it yourself though. you will need someone to help with some fabrication if you build yourself though. otherwise, you are just buying off-the-shelf parts and piecing together a generic kit.