Inon O-ring set for Inon Strobes - S-220 - Z-330 - Z-240 -S-2000 - D-200 and D-2000. All kits now have the sync connector cap o-ring included even if your strobe does not have a sync connector
INON yellow O-rings contain lubricant in the o-ring rubber. Yellow color for best contrast, so contaminants etc. are easier to see, and so it is harder to forget to install the O-ring