Abstract: A known kind of spring unit, for use in mattresses, seats and the like, is made as an assembly of spring bands which are disposed side by side and a plurality of helical wires (5,6) which extend transversely to the bands and are linked to them. Each spring band comprises a row of springs (1), and each pair of adjacent springs is integrally connected by a connector (2) which includes two spaced end portions (3), which are transverse to the band and are embraced by helical wires. Variations in manufacture lead to variations in the spacing between the end portions. The invention provides for the further bending of each connector (2), after initial formation of the spring band, to cause the end portions to take up a predetermined spacing. This is effected by reshaping corner portions of the connector between dies (31,42) so that the corner portions (8) are finally of more gentle curvature than they were (12) when initially formed.