Grapefruit of good quality are firm, springy to the touch, not soft, wilted, or flabby but well shaped and heavy for their size.  Fruits heavy for their size are usually thinned skinned and contain more juice than those that have a coarse skin or are puffy, or spongy. Decay is sometimes evident and should be avoided as it affects flavor making it flat and somewhat bitter.  Decay may appear as a soft discolored area on the peel at the stem end, or may appear in the form of a water soaked area, much of the neutral yellow area being lost, and peel so soft and tender that it breaks easily with finger pressure.  Fruit somewhat pointed at the stem end is likely to be thick skinned, particularly if the skin is rough, ridged or wrinkled.