The GAP 4 package Cryst, previously known as CrystGAP, is the successor of the CrystGAP package for GAP 3. During the porting process to GAP 4, large parts of the code have been rewritten, and the functionality has been extended considerably. Cryst provides a rich set of methods to compute with affine crystallographic groups, in particular space groups. In contrast to the GAP 3 version, affine crystallographic groups are now fully supported both in the representation acting from the right and in the representation acting from the left. The latter representation is the one preferred by crystallographers. There are also functions to determine representatives of all space group types of a given dimension.