This system uses wafers of silicon 150 mm in diameter and about 1/2 mm thick.
Wafers are loaded into a cassette that stacks the wafers on top of "C" shaped fingers. The fingers are designed to hold the wafer only on its left and right edges.
For clarity, this illustration shows a single wafer and a cassette with five layers of fingers. The real cassette has 10 layers, allowing 10 wafers to be loaded at once.
The loaded cassette is placed within the "Fast Entry Loadlock" and the door closed.