Biconcave shape of RBC’s is helpful because:
Guyton-419
Normal red blood cells, are biconcave discs having a mean diameter of about 7.8 micrometres and a thickness of 2.5 micrometres at the thickest point and 1 micrometre or less in the centre. The shapes of red blood cells can change remarkably as the cells squeeze through capillaries.
Easily passage through capillaries
Roulex formation.
Increased surface area for a given diameter.
None.