The Iris upgrade for RT Motion hand units replaces the iris scale making it toollessly interchangeable.
The stock RT iris marking area is screwed onto the unit and only comes with one scale, so when you change to a lens with different markings you have to either re-draw all the marks or peel and stick marks on tape over and over. In our opinion that just doesn't cut it. This solution allows ACs to pre-mark all of their lenses before the shoot. During a lens change, ACs will be able to quickly and toollessly swap iris markers.
Two index holes make swapped iris markers return to the same place each time ensuring repeatability and accuracy of the iris markings throughout the shoot.