Three sheets, A4, 153 g/m2. Yupo is paper that is not paper.
100% polypropylene, recyclable, translucent, acid-free, tree-free, stain-proof, extremely durable and erasable.
Excellent for experimental work with watercolours, all kinds of inks, oils and acrylic. Also good for fiber pens, brush markers, acrylic markers etc. 
Treat yourself to a 3-sheet experiment and see what you can create.