Yes, it’s Roy Walton’s classic trick where one card folded inside of another magically turns inside out.
But was it magic, or did you use the power of your mind to accomplish that? (Seriously, if metal bending can be considered mentalism, then cardboard bending for sure could be mentalism. Couldn’t it?)
If you don’t do Card Warp, download the PDF document below and give it a look anyway — it may spark some ideas for reframing some of the magic you do as mentalism.