I posted this in another thread, but I think it's of use here, also. Please forgive me for the multiple
posting ---


BikeToolsEtc has a nice little reference cheat sheet in their catalog for replacing caged balls with loose. I will paste it up here:

" Component Loose Bearing Sizes (Exceptions Exist)
Components..................Size..........................Bearing Count
Bottom brackets.............1/4".........................11 each side
1" headset.....................5/32".......................25 per cup
1 1/8" headset................5/32 or 3/16"............20-28 per cup
1 1/4" headset................5/32 or 3/16"............26-31 per cup
front hub........................3/16"......................10 per side
rear hub.........................1/4"........................9 per side
pedals............................5/32 or 1/8".............10-15 per side
SPD pedals.....................3/32".......................lots
If in doubt, fill space with bearings and remove one.
It is possible to replace the balls in a bearing retainer that's in
good shape. Just pop 'em out and pop in new ones of the same
size. "


As they say, "exceptions exist", but I have yet to find one myself.
It's a pretty good list.