The Metabones/Viltrox Adapter Lock secures lens adapters to the XLCS Cage, eliminating potential mounting failures and relieving strain on the native mount. Machined from high-strength aluminum and anodized black, it's compatible with Metabones, Viltrox and other various basic adapters. This is the cleanest way to adapt lenses to your Sigma FP
 
Also Compatible with most other XLCS Design Cages.
 
FOR SIGMA MC-21 ADAPTERS, PLEASE SEE THE SIGMA MC-21 SPECIFIC LISTING
Includes: Adapter Lock, Mounting Screws and Hex Wrenche