These are simplistic cubic extensions to turn a normal 3x3x3 Rubik's style cube into a cubic crystal shape-mod. I used a 40mm mini cube for mine but 30mm and 35mm are easier to find, so you will need to scale appropriately to fit your cube.
Simply attach the two cube extensions to your centers, and the one cube extensions to your edge pieces. You'll need 6 center extensions, and 24 edge extensions total.
I have also included a sticker template if you so desire to cut your own stickers. Again, make sure to scale appropriately.
I also recommend sanding the inner surfaces with a fine sanding sponge to remove friction.