Thanks, that's a good pic. I would guess those are 0.010" wire. They look OK with the factory handrails, but if I were doing a detailing project with custom wire handrails I would use 0.008" wire for the handrails and 0.005" wire for the grabs. (Replacing wire grabs is a bit easier than shaving off cast-on grabs, but you still have to fill the oversized holes with matching paint.)
Ed