Very disappointed that there was no advice at purchase on the need for a mat or pad. Subsequently ordered one and the performance is too jittery for cad work. It is even difficult to use word or outlook. There is reference to change of sensitivity between 400 and 4000dpi which may be the problem, but talking to tech support this in fact can NOT be altered. Pointer speed can be changed but this is not the same thing. As somebody running a team of cad users I'm always looking for tools to aid productivity. This sadly is not fit for purpose and I will be returning it to the retailer. As a user of Logi tech for many years I am extremely disappointed.