Headset bearings - help!

All,
I am looking at buying some bearings for a Campag Chorus headset on a 1" threaded fork. Bearings are loose and not in a cage.
My question is what size do I need to buy as there are so many to choose from -
1/8" Ball Bearings
5/32" Ball Bearings
3/16" Ball Bearings
7/32" Ball Bearings
1/4" Ball Bearings

Thanks very much

Think it depends on what headset you have

The headset is a campagnolo chorus headset which I think is around 1988.

Pretty sure it's 3/16''

Twenty if they are in a cage, or more if you have them loose.

That's great @Poetic, I'll go for those

Could you bring one of the old bearings to your LBS, they should have a bearing measurer, a sort of ruler with holes for gauging the size of different bearings.

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Thanks very much for the information , I have bought some 3/16'' as per @Poetic advice and will go from there.

Worth measuring them properly, it's almost impossible to tell by looking at them, plus campagnolo headsets sometimes use different sized bearings for the top and bottom cups.

For the sake of a few quid it would be worth getting a vernier and save screwing up a potentially expensive and nice old headset