For Sigma 14-24mm f/2.8 DG HSM Art Lens, Enables Use of SW150 Mark II Holder, Secure Attachment to Lens, Easy Installation, Aluminum-Alloy Construction. This LEE Filters SW150 Mark II Lens Adapter is designed to allow a separately available SW150 Mark II Filter Holder to connect to a Sigma 14-24mm f/2.8 DG HSM Art Lens which then permits the use of 150mm-wide 2mm-thick filters without vignetting. This lens adapter consists of three components: a front ring a compression ring and a locking ring. Placement of the lens adapter onto the lens is easily accomplished by sliding the front ring over the built-in hood with the front ring's integrated lugs positioned away from the lens body. The compression ring can then be slid over the rear of the lens until it meets the front ring. Finally the locking ring is also slid over the rear of the lens until it can be screwed into the front ring. After that is accomplished an SW150 Mark II Holder can be placed over the adapter from the front of the lens for use.