OK, I’ll admit the title “TRX Travel System” and a pic of various straps and gadgets got me here. What could that be?
But exercise? Interest lost. 
Pro tip: Use caution when using the door connection if your door opens toward you… Ouch.
These are really kewl, and it is amazing the workout you can get using your own body weight. I made on myself from boat rope and a nylon belt. It was functional, but it hurt my hands, even with gloves on. This one would be fantastically useful.
LOL! Those hollow core doors aren’t very strong either.
No Pain. No Gain!
woops, defo clicked reply on the wrong comment. meant that for the door opening on yourself lol.
Do not use this for repelling, ouch!
These things are fantastic, particularly useful for stretching arms/back/legs using your bodyweight. Seriously, more useful than you might think. However, there are off-brand versions of the same quality for much less on amazon.
These things are fantastic. I used them in the Navy for years to work out in confined spaces, and still have several sets that I use today. highly recommend.