This may be futile but I'm gonna post a heads-up warning here.
I have been noticing the outermost edge of some of my keg lid O-rings are cracking - badly - enough that the cracks may soon extend to where it matters. I have 16 five gallon kegs in service (along with a 3.5 and 3.5) and figured I better stock up on some O-rings to start swapping out the cracked ones.
There's a person on Amazon that has competitively priced cornelius keg O-ring sets ($1.80/set) that include lid, dip tube, and both ball lock and pin lock post O-rings. The seller has listings with differing quantities but the words "Stir-Plate" and "Home brewed with pride" appear in his placements to help identify them.
One of his listings is
here, this one for 10 sets of O-rings. And if you look at the provided image you see an array of BLACK O-rings...
View attachment 842685
...which is a good start if you're hoping for Buna-N/Nitrile (same stuff/different names) - though I could not find any statement in the listing as to the actual rubber used. I relied on Amazon's good graces to cover my ample @ss on that.
Anyway, what actually arrived (three days late, but that's on AMZL) looked like this:
View attachment 842686
Alarms immediately went off - I definitely do NOT want silicone O-rings on my kegs - so I sent the seller a message via the AMZ portal asking what material was actually used in the set. His response was they were
all SILICONE - and phrased in a way that made it seem this was a change from what he used to sell. So I explained why I'd be sending the package back immediately in favor of actual Buna-N O-rings.
After looking around on Amazon I found this listing for 10 sets which outright states
Buna-N, so hopefully the next purchase will work out.
https://www.amazon.com/dp/B07Z5GQ77P
Be careful out there...
Cheers!