 Radial artery is smaller in caliber compared to femoral artery with mean size reported at 2.44 mm. Women and persons of south Asian descent tend to have smaller radial arteries with means of 1.91mm and 2.00 mm respectively. Outer diameters of commonly used 5F and 6F sheaths are 2.16 mm and 2.62 mm respectively. Ratio of radial artery to sheath size affects post-procedural radial artery flow. 