This special package offers four tests, including Electronic von Frey, Plethysmometer, Randall Selitto meters and the Grip Strength Meter. You get all four test modules and the electronic controller that is interchangeable with all four systems. The electronic controller has up to three inputs, so you can perform up to four unique tests with only one electronic system. If you prefer, you may build your system and you grow. Because of the modular design of these four systems, you need to order only one complete system. Then, the modules for the other three tests, which integrate into the system, can be purchased separately, as needed. The stand and sling for the Randall Selitto test are sold separately.