This socket accepts 14-18 AWG stranded wire — that's the range you need to match to your harness BOM. Tin-lead plating on the contact body means the crimp barrel will take solder if needed for a secondary bond, but the primary retention is mechanical through the crimp.
Plating and Compliance Reality
The tin-lead finish on the 66601-7 is a lead-bearing plating — not RoHS compliant by default. If your assembly requires RoHS, you'll need the tin-plated variant from the same series. No specific UL or VDE rating is listed for this contact alone — the approval sits at the mated connector assembly level.