25 Count Lugana Fabric is recommended for experienced stitchers because it's very fine - just 100 stitches per 10cm. 
Due to this finest a high presicion is achieved, often compared to a drawn picture. You can stitch petite stitches and 3/4 stitched on this linen evenweave to achieve smoother contours.
Also, due to this weaving, the non-stitched part of the work looks like a fabric without visible holes.