Chamonix now has the Iris diaphragm style variable diameter lensboard. It has a max opening of 94mm with usable mounting opening of 90mm. The smallest aperture is 25mm. The weight is 230 grams (8.11 oz). The outside diameter is 98.2mm, it can be used on the Sinar style lensboard.

If you need it mounted on a Sinar aluminum lens board, add $60.