Insertion devices, as well as beamline front-ends, are continuously being modified to satisfy the evolution and refurbishment needs of the beamlines. In 2004, the first prototype revolver undulator was installed on ID18 and successfully commissioned, and a second one has been installed on ID10. Such a revolver structure allows the beamline users to switch from one undulator period to another in matter of seconds. A number of conventional undulator segments were refurbished to make full use of the new 10 mm high aluminium vessels which are gradually replacing the stainless steel 15 mm and 10 mm chambers. The beamline front-ends are being refurbished at a rate of 4 beamlines per year, making use of every shutdown. The "high power" design allows the operation of a 5 m long undulator at a minimum gap of 11 mm with a stored current of 200 mA, or alternatively a 4 m long in-vacuum undulator at a minimum gap of 6 mm.