Haida Rear ND Filter Kit for Sigma 12-24mm f4 & 14-24mm f2.8 (Canon EF Mount) | eBay
NiSi Sigma 12-24mm f/4 HSM ART Series Adapter for NiSi 180mm Filter Holder (Discontinued) | NiSi Optics USA
Sigma 12-24mm F4 DG HSM Art vs Sigma 12-24mm F4.5-5.6 EX DG Aspherical HSM Detailed Comparison
Sigma 14-24mm f/2.8 DG HSM ART Lens for Canon EF 212954 - Adorama
WonderPana XL Filter Holder for Sigma 12-24mm f/4 DG HSM ART Lens (Can – Fotodiox, Inc. USA
NiSi 150mm Filter Holder for Sigma 12-24mm Art NIP-FH150-SI1224
Aluminum 150mm Square Filter Holder Bracket Support For Sigma 12-24mm F/4.5-5.6 Ii Dg Hsm Compatible For Lee Hitech 150 Filter - Camera Filters - AliExpress