Information from website:
SKU # 36122 New cost $202.00
Zoom gears allow access to the mechanical zoom function of supported lenses.
Use of this gear may require the use of additional port extensions or adapters.
Check the Port Chart for more details.
PLEASE NOTE: SMALL RUBBER PIECES USED TO INCREASE FRICTION IN BETWEEN
GEARS ARE MISSING (LOST IN THE SPACE), BUT YOU CAN USE ANY STICKY TAPE
INSTEAD OR ORDER THESE RUBBER PIECES FROM REEF PHOTO IN FLORIDA FOR
A COUPLE DOLLARS.