The focal length should be 210mm, and the distance between the magnifying glass and the text should not exceed 210mm to avoid eye dizziness.
Full Page Sheet Magnifier 180×120mm Reading Aid Lens Large Magnifying Glass
"Full Page Sheet Magnifier Reading Aid Large Magnifying Glass Lens"
Full Page Sheet Magnifier Reading Glass Large A4 Magnifying Lens Aid Book Reader
Large A4 Sheet Magnifying Glass Full Page 3X Magnifier Reading Aid Lens Big UK
A4 Full Page 3x Magnifier Sheet Large Magnifying PVC Glass Book Reading Aid Lens
