What are the key grape varieties used in Bordeaux red blends?

Bordeaux reds are a blend of several key grape varieties which include Cabernet Sauvignon known for its bold tannins and dark fruit flavours, Merlot prized for its plush texture and ripe fruit character, Cabernet Franc adding aromatic complexity and herbal notes, Petit Verdot contributing colour, structure and spice and Malbec providing depth of colour and plum-like flavours.