Just wanted to clearup some mis-information and add to the plethora of information here on Zilvia, the B12 Sentra ball joints are what you people need.
I picked up a pair off ebay for a steal of a price from "partsdepot1" in Canada, excellent reputation - quick shipping, got exactly what I paid for. From my inspection I cant see anything wrong with the quality of these ball joints, plus they came with grease fittings which I will absolutely not complain about!
I will do a side-by-side comparison next week just to confirm, but my caliper measured these at 38.3mm
Keep the shiny sides up.