A tread for a pneumatic tyre , the tread comprising: a plurality of grooves , the grooves comprising: a groove surface ; and a plurality of elements spaced from one another in an arrangement on the groove surface ; wherein each element has a shape defining a volume, the shape including: a first cross-sectional shape in a plane parallel to the groove surface , wherein a smallest dimension of the first cross-sectional shape defined at the groove surface defines the width w of a base of the element , wherein 0.1 mm ≤ w ≤ 3 mm; a second cross-sectional shape in a plane perpendicular to the groove surface , wherein a greatest dimension of the second cross-sectional shape from the base at the groove surface to a top defines the height h of the element , wherein 0.1 mm ≤ h ≤ 3 mm; and an aspect ratio of the height h divided by the width w of at least 1 and up to 30; and wherein the arrangement comprises: a void volume in the spaces between the elements ; and characterised in that : the second cross-sectional shape is generally parabolic or hyperbolic; and the arrangement comprises a void ratio of between 0.5 to 0.75, wherein the void ratio is defined as a ratio of the void volume to the total volume of the elements in the arrangement, wherein the void volume is defined by the total available area between the elements multiplied by their height h. a groove surface ; and a plurality of elements spaced from one another in an arrangement on the groove surface ; wherein each element has a shape defining a volume, the shape including: a first cross-sectional shape in a plane parallel to the groove surface , wherein a smallest dimension of the first cross-sectional shape defined at the groove surface defines the width w of a base of the element , wherein 0.1 mm ≤ w ≤ 3 mm; a second cross-sectional shape in a plane perpendicular to the groove surface , wherein a greatest dimension of the second cross-sectional shape from the base at the groove surface to a top defines the height h of the element , wherein 0.1 mm ≤ h ≤ 3 mm; and an aspect ratio of the height h divided by the width w of at least 1 and up to 30; and wherein the arrangement comprises: a void volume in the spaces between the elements ; and characterised in that : the second cross-sectional shape is generally parabolic or hyperbolic; and the arrangement comprises a void ratio of between 0.5 to 0.75, wherein the void ratio is defined as a ratio of the void volume to the total volume of the elements in the arrangement, wherein the void volume is defined by the total available area between the elements multiplied by their height h. a first cross-sectional shape in a plane parallel to the groove surface , wherein a smallest dimension of the first cross-sectional shape defined at the groove surface defines the width w of a base of the element , wherein 0.1 mm ≤ w ≤ 3 mm; a second cross-sectional shape in a plane perpendicular to the groove surface , wherein a greatest dimension of the second cross-sectional shape from the base at the groove surface to a top defines the height h of the element , wherein 0.1 mm ≤ h ≤ 3 mm; and an aspect ratio of the height h divided by the width w of at least 1 and up to 30; and wherein the arrangement comprises: a void volume in the spaces between the elements ; and characterised in that : the second cross-sectional shape is generally parabolic or hyperbolic; and the arrangement comprises a void ratio of between 0.5 to 0.75, wherein the void ratio is defined as a ratio of the void volume to the total volume of the elements in the arrangement, wherein the void volume is defined by the total available area between the elements multiplied by their height h. <EOS>