The meter base size determines which size service conductor you need to purchase. Typical service conductors include:

Service Rating    Maximum Distance     Conductor
200 amp              220 feet                       4/0–4/0–2/0 Aluminum (1 run)
200 amp              250 feet                       250–250–3/0 Aluminum (1 run)
200 amp              340 feet                       350–350–4/0 Aluminum (1 run)
320 amp              220 feet                       4/0–4/0–2/0 Aluminum (2 runs)
320 amp              250 feet                       250–250–3/0 Aluminum (2 runs)
320 amp              340 feet                       350–350–4/0 Aluminum (2 runs)