Abstract: A pallet for automatic production lines, comprising a base (1) on which a guide (5) is mounted on which support arms are engaged for a workpiece (16). The arms (13) allow a movement on a transverse plane with respect to the axis of guide (5) between a first and a second position, in particular a rotation movement. In the first position, the arms are able to either translate along the guide or be moved away from it in a transverse direction, in the second position the support arms auto-lock onto the guide through resilient means (21). The pallet has therefore variable distance support arms which are able to auto-lock onto the guide and are easy to be unclamped by it without requiring neither separate locking/unlocking devices, nor, consequently, regulation means able to interact with said devices. The pallet can be adjusted with no modifications to operate both on a line with a station of automatic regulation and on a line with a station of manual regulation.