Personally, I would have gone with "the size of a trade paperback". Or maybe "the size of a large hardback book held with the arm fully extended." Honestly it

Personally, I would have gone with "the size of a trade paperback". Or maybe "the size of a large hardback book held with the arm fully extended." Honestly it sounds really small. Not sure how you could have a viable product that only works in a small rectangle in the center of your vision.