The LEE100 Tandem Adapter allows two LEE100 holders to be joined together and rotated independently from each other. This is a totally unique feature of the LEE system; no other filter system on the market can do this.The adapter slides into the front slot of the first holder and then the second holder clips onto the adapter in the same way it would to a LEE100 adapter ring.The LEE100 Tandem Adapter is ideal for: Landscape photographers who need ND grad filters positioned at different angles. For example, if you had bright side light on one side of an image you would need to position one ND grad filter vertically to hold back the brightness. Whilst another ND grad filter would need to be positioned horizontally to hold back the detail in the remainder of the sky. Another example is if you were shooting down a valley or a scene with a mountain peak. You can position the ND grad filters so that they line up with each side of the valley, or if shooting a mountain peak they can be positioned either side of the mountain. Fashion / portrait photographers can also use the technique of having ND grad filters at different angles. An example being ND grad filters positioned either side of a models face, for a darker moody looking image.Features and benefits of the LEE100 Tandem AdapterEasy to positionThe adapter simply slides into the furthest slot of the first holder. Two small lugs on either side o