The ESRF insertion devices are the object of a continuous refurbishment in order to follow the changing needs of the beamlines and increase their performances. The successful development of the narrow aperture aluminum chambers pumped by non evaporable getter has resulted in the reduction of the minimum gap from 16 mm to 11 mm . A new set of undulator magnetic assemblies with shorter magnetic periods are being prepared that make use of the lower gap. .A prototype of a new type of revolver

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... tor support has been completed and successfully tested. Such a structure allows the beamline user to switch between two different undulator periods in less than a minute. Three additional devices will be constructed in 2004. Three new invacuum undulators have been installed on the ring. One of them is based on an hybrid magnetic structure and achieves a peak field 20% higher than a pure permanent magnet undulator of identical period. Their main magnetic measurements results and interactions with the stored beam are presented.