If you're a fan of bodyweight workouts, you'll dig muscle rings. Similar to suspension trainers like TRX, muscle rings are versatile, portable and, more importantly, let you get a fierce upper body workout anywhere. Muscle rings, also called gymnastic or Olympic rings, are two long straps with giant rings on each end. Just like suspension trainers, you can set them up from any tall anchor point, such as pull-up bar or a tree branch. Each ring moves independently and can also be set at different heights for a challenging workout.
Since these are also used by gymnasts, muscle rings are great for emphasising upper body strength, but are a bit more limited in lower body exercises and not as beginner-friendly as suspension trainers are. If you have something like the TRX already, there's not a whole lot of reason to also get muscle rings, unless you want to work on gymnastic-specific movements.
Why You Should Use Muscle Rings For Your Workout [Calisthenic Movement]