Here are the listings from the Orvis catalog . . . if the diameter spec is without line, then the 4" diameter is appropriate.

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VO2 III Reel: For line weights 4-7. 6 3/8 oz., 3 11/16" diameter (SI77LK-61)

VO2 IV Reel: For line weights 6-9. 9 1/8 oz., 3 15/16" diameter (SI77LE-61)

VO2 V Reel: For line weights 8-11. 10 oz., 4?" diameter (SI77LG-61)

VO2 VI Reel: For line weights 10-13. 11 15/16 oz., 4?" diameter (SI77LH-61)
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Interesting observation: at 40 mph, a fish will pull about 60 feet of line per second from your reel. That must be like fighting a carp.

CARPE CARPIO (sieze the carp)