This idea was a breakthrough for stage mentalism, and later on Jeff Busby and Gene Nielsen created a Zip-Loc-like model.
This one is also a Zip-Loc-like model, but it has 3 compartments instead of 2. The red line will help you to know which side you are using.
If you want to use 2 compartments only, close the Zipper of one bag, and that's it, now you have a regular double force bag.
Dimensions Approximately: 13" x 9.5"