The ultimate rock alpha pack contains over 100 high quality 4096x4096 16 bit rock alphas in various file formats. It also comes with detailed substance graphs showcasing how to utilize these rock alphas to generate high quality materials. Finally it includes marmoset preview files to see how I've set up the renders of these materials.

Furthermore these rock alphas can be used in Zbrush, Substance Painter, or any other program that can utilize alpha based images.