TargetTalk

A maintenance question: The o-ring that seals the cylinder onto the inlet valve (circled red below) failed on my K2S. I'm not exceptionally bothered by this; it's a wear part since I have to constantly screw the cylinder on and off for refills and I do have a couple spares, but I'm curious how often this really should be replaced. Every air pistol will have something like this, I'd imagine. What do you think is a good interval to replace this?

When it fails? With lubrication and care to keep them clean, I've had plenty that lasted a decade or more.

I replace mine when they fail.
If you measure the one you have, you can buy a bag of 100 from McMaster Carr for $3.50.
Get the "high durometer" version and a little dab of Super Lube from Ace hardware.

I use a silicone based light oil and I never have had to replace an o ring. Not even the breech seal O ring on my 777 bolt that sees far more wear than this one.....