Continuous text letter sizes range from 20/100 to 20/20 (6/30 to 6/6) equivalent in each contrast level. ETDRS, format letters sizes range from 20/400 to 20/10 (6/120 to 6/3) equivalent in 17 increments for each contrast level. Each contrast level page is tabbed for easy access with included instructions. Printed on durable long-lasting styrene plastic and clear coated for added protection. This near vision contrast booklet contains 7 pages measuring 6.25" x 6.25" (15.8 cm x 15.8 cm). Testing distance: 16"/40 cm.