WonderPana 145 Essentials ND Kit - Core Filter Holder with ND16 (4-Stop) and ND32 (5-Stop) Filters for Sigma 8-16mm f/4.5-5.6 DC HSM Ultra-Wide Zoom Lens Premium Grade Anodized Aluminum WonderPana 145 Core Unit for the Sigma 8-16mm f/4.5-5.6 DC HSM Ultra-Wide Zoom Lens Slim double threaded ND16 & ND32 filters; made of high quality optical glass Perfect for landscape photography and long exposure photos 145mm x 1mm standard filter thread enables filter stacking (other Fotodiox 145mm filters; UV,MC-CPL,ND4/8/16/32/1000); heavy duty inner-pinch cap included 24 Month Manufacturer Warranty