Yes, I’ve been using Chris Sommer’s book. I do have a pair of rings, but I haven’t used them yet, too advanced for my current levels. But they’re there when I’m ready for them. Thus far the only equipment I have used is a pull-up bar, dips bars, and the floor (push-up handles help take the stress off the wrists). That’s one of the reasons I like the exercises, you can build and maintain serious strength with virtually no equipment. It’s about as low tech as you can get.