4.4 Thickness gauge, with an accuracy of ± 0,01 mm (see ISO 23529:2004, 7.1), having a flat circular foot 4 mm ± 0,5 mm in diameter and a flat solid base-plate and exerting a pressure of 22 kPa ± 5 kPa for solid
rubber of hardness equal to or greater than 35 IRHD or a pressure of 10 kPa ± 2 kPa if the hardness is less
than 35 IRHD. For comparative tests, the same dimensions of the circular foot shall be used.