Thought that title would get people looking :P

I've just bought some old Nissin 4 pot front calipers of a GSXR600 SRAD (don't know what year - long story short they'd been fitted to another bike) but the bleed nipples are missing. The nips off my Tociko 6 pots don't fit.

Does anyone know what size nipples I need (now there's a leading question)?

Cheers,
Steve