In the field of underground works, accuracy is not optional: it is an essential condition for safety, durability and performance. Tunnels, whether railway, road, metro, or for water and energy networks, must meet significant geological and technical constraints. Each segment, a constituent element of the final ring, must be dimensioned and manufactured with extreme rigor. It is within this demanding context that CBE, a specialist in segment moulds and automated precast plants, has built over nearly 40 years a unique expertise in manufacturing tolerances.