The high tensile yo-yo 5272 PROOF gadget appeared in the novel Stormbreaker.
This hi-tech yo-yo is a miracle of miniaturized engineering and was designed to aid climbing - its powerful winch action and strong cord made from super-tough carbon fiber could lift anyone's weight easily. However, not even Smithers could have foreseen how Alex Rider would use it.
The yo-yo was used by Alex Rider in the novel Stormbreaker, and also in the movie adaption of Stormbreaker.
He had used it to climb onto a plane, by letting it pull him into the rooms after tying it to a harpoon into the door. To read more, go to the "Stormbreaker" plot.