Just a first impression, but this product looks ridiculous. The body mechanics of trying to lever yourself into a pull up facing a closed door seem very awkward, and would probably require a lot more strength than a normal pull up.
And that’s if your elbows don’t put holes in your hollow interior door first. Pictures look nice though.
I have to mention the fact that no door is meant to hold up the weight of a person, at least not the average door in most homes. I have not tried this product but have used other products that place weight on a door and after some time it will cause issues with door alignment, etc… Yes a door is at its most stable when closed, but this or anything that is used to hang weight on a door will eventually cause problems. Fair warning if used in this way.