The length of a round strap shall be not less than 40 % of the circumference of the codend, the circumference being measured as the product of the number of meshes in the circumference of the codend multiplied by the actual mesh size, except for the rearmost round strap called 'back strap' if it is attached not more than 2 metres from the codline meshes, measured when the meshes are stretched lengthwise.