Both in pencil: 4B for the softer lines and shading, with some HB where sharper lines are needed). Top one's a bit bigger than A3 (that white line is the fold of the sketchbook), and the lower one is a bit smaller.
I've been looking at this book: British Museum Master Drawings in Close-Up, particularly the Raphael drawing that's on the cover.
(Clearer image on the BM website: Raphael drawing)
To get the shadow tone, I think he's smudged the chalk, and then gone over it again with hatching lines. Those lines go the same way: they don't follow the shape or volume of the body (just a bit round the waist), and there's hardly any cross-hatching.
What really gives the drawing life is the variation in the lines that make up the outline. Every line curves and moves; the strongest lines are where there is contrast between light and dark (on the arms), and the stressed parts of the body (the bent knees); and he hasn't bothered to rub out the light preliminary lines.
