Standard Size: 175 X 180 X 70 mm (145 X 35) [(L * W* H) (d*h)] mm in which L = Length; W = Width; H= Height; d= inner diameter; h = median height dimensions in milimeters. 
Relieves skull compression from head / calf in supine position (like eye surgeries) by providing cross-sectional stability
Contoured to match the anatomical shape of head by pressure redistribution in all directions