The Arri Matte Box MB-20 II is designed for light weight mini-rods. It's modular mounting options allow it to attach to most lenses as a clamp-on, or it can utilize standard 15mm support rods.
All of the MB-20 "Back End" accessories fit the MB-20 II, including the Clamp-On attachment Clamp rings and all of the bellows rings found on the MB-20 quick guide.
The biggest differences between the MB-20 and the MB-20 II is in the attachment mechanism between the actual plastic matte box and frame, and the attachment hardware for the eyebrows and side flags. The MB-20 uses the design from the MB-19 and the MB-20 II is an all new design.