Should I use sanded or non-sanded grout?

The rule used to be to use non-sanded grout for joints 3mm or less and to use sanded grout for joints bigger than 3mm. However, today there are universal grouts available that are produced with finer sand particles and will work for most joints. These “New Generation” grouts are so fine that they can be used with glass mosaics, wall tiles and many polished stone tiles without scratching the surfaces.