First you have the standard Vertical Mouse 4 for right-handed or left-handed users (models VM4R and VM4L). This is the newest model of their famous mouse first produced back in 2001. Numerous enhancements have been made to the deisgn over the years and it is still one of the best-selling ergonomic mice available today.
In addition to the standard models Evoluent also offers a "small" version and a wireless version of the right-hand model (cordless unit shown in picture above).
The new wireless model (VM4RW) boasts all of the same features and benefits of the standard unit plus a 2.4GHz mini USB receiver that has a very low profile, which means it's going to stay in your USB port and not be knocked out by accident.
The small version (VM4S) was made specifically for users who have a hand size less than about 7". Hand size is determined by measuring the length from the crease of your wrist to the tip of your middle finger. If your hand is less than 7 inches it is recommended to go with the small model for the best fit.
Evoluent has also released a new version of their compact computer keyboard (model EKB) and they continue to also offer their ARMazing memory foam arm pads for your chair.