I remember starting off as a little RDM and getting flattened by these guys...and a made a vow that I'd come back when I was stronger and kill them all. Now they go down in a single hit. How times change.
The higher level versions of these in Ghelsba Outpost and Ghelsba Fort will drop randomly: Bronze Leggings Bronze Cap Bronze Subligar
I'm not sure, but I think they might drop all the bronze armor pieces if you kill enough, those are just the three I know I've gotten off of Grapplers.