The invention relates to a device (1) for the continuous lengthening of a metal strip (2) by traction, said device comprising, in the strip transporting direction (R), at least three S-roll units (3, 4, 5, 6, 7) each provided with at least two rolls (8, 9, 10, 11, 12, 13, 14, 15, 16, 17). According to the invention, the rolls (8, 9, 10, 11, 12, 13, 14, 15, 16, 17) are positioned in such a way that the metal strip (2) is wound round them at a roll periphery angle (a) of more than 180°, and at least the second S-roll unit (4) in the strip transporting direction (R) comprises two rolls (10, 11) with different-sized diameters (D10, Dn).
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