The ratio of large to small squares is 9:1. Originally designed for hematology, they can be utilized for rapid counting of any evenly spread field of particle. References: American J. of Clin. Pathol. Vol.20, 1950, page 1079. "Time Saving Device For Counting Reticulocyte." G.Brescher and Schneiderman. Practicle Haemotology – J.D. Dacy. Published by J.A. Churchill. 2nd Edition 1956 page 25.
Size: 19 mm
Divisions: 9:1 Large to small square
Surface: Glass sandwich