I also think your spherical shell (for the infinite transformation) is quite narrow. It would be better to set the exterior radius to 470e-3 instead of 370.e-3. -- Christophe Geuzaine Tel: +32-(0)4-366.37.10 mailto:Christophe.Geuzaine at ulg.ac.be Fax: +32-(0)4-366.29.10 http://www.montefiore.ulg.ac.be/~geuzaine/