Just bought some greys (secondhand) with o rings on the bottom but with none on the top.

Would it possible to take the o rings of my greens to put on the greys?

Or is it that once fitted they cannot be used again if taking of.

 

The o rings will be fine to reuse.
tabetha

 

i think you need the fitting kit unless the greys have the metal coller still fitted to them.