"Number Rack" You can adjust how many strings of beads you have showing up to 10 strings. The movement of the beads is pretty similar to the actual rekenrek. It's nice that I can pull beads to the right at the same time I'm sliding beads to the left. It also lets me slide a whole group of beads over at once. It has a screen, but I can't seem to be able to move the beads under the screen like I could with a real rekenrek. However, you could use the screen to decompose a number. If 3 beads are showing, how many beads in the string of 10 are hidden under the screen, etc.
Want to see the rekenrek in action? Check out this video on Youtube created by Bill Davidson. He was one of the presenters that came to Albany to share information about the upcoming math modules. In less than 5 minutes you can see many ways to use a 20 bead rekenrek... enjoy :)