We have created the C6 Web Tool that uses an underlying metric to compare the chemical similarity of two crystallization conditions and by extension the similarity of two crystallization screens. With over 220 crystallization screens currently available for purchase, it is difficult to know what each screen contains and when it is appropriate to use that screen. The C6 Web Tool can be found at
http://c6.csiro.au and is available to the crystallization community at no charge. In addition to measuring the similarity of conditions and kits, the C6 Web Tool also provides the means to examine the conditions of a crystallization kit (or kits) in novel ways. Using the C6 Web Tool, researchers can efficiently select appropriate screens to use throughout the various stages of a crystallization project.