This is sort of a mini-review, because there’s not a whole lot you can say about something as simple as O-rings. But I thought you’d like to know that Tantus makes O-rings now and they’re great.
They’re significantly stretchier than any others I’ve tried. They come in a huge variety of sizes, ranging from 1.2” to 2.5” in diameter. And they cost only $20 for the whole set of 6 rings. $20 is a pretty reasonable price for never again needing to worry if a particular dildo will fit into your harness.
(If you need a harness that will work with all of these O-rings, I heartily recommend the Aslan Jaguar!)
All in all, these O-rings are a very good buy for anyone who likes strap-on play in any configuration.