Sigma Drop In Filter Holder RFH-21 L-mount

Sigma Drop In Filter Holder RFH-21 L-mount - a drop-in filter holder that supports commercially available φ40.5mm filters. The included drop-in filter holder, and the separately sold C-PL and variable ND filters are designed specifically for each mount. Please be careful when purchasing so that you choose correct filter for correct mount. Compatible with: Sigma 300-600MM F4 DG OS SPORTS L-mount.