The slide is made in Acrylic. 1 mm x 1 mm Gridded design is used for counting larger plankton. Intended for use with a standard or inverted compound microscope at low magnifications ( up to 200x ). The 1mL counting cell measures 7.10 x 3 inches ( approx ) The cell of 75 x 30 x 1 mm is ruled in a 1 mm grid subdividing 1 mL in 1000 µlit is a single type