The VALOI 360 Film Mask for 35mm Half-frame is made specifically to fit into both the Advancer with the Holder on top or under the Holders if you use them without the Advancer. This is an optional accessory for scanning smaller formats.
Blocks off stray light when scanning smaller formats.
While the Holders can accommodate smaller formats, some setups might struggle with stray light causing flare in the lens or reflections down onto the film. In these cases, the masks mask off excess light if you are scanning a smaller format than the Holder's maximum size. It is not necessary for everyone but can be extra security if you want a clean a scan as possible.
To use the mask, you must therefore buy the appropriate holder as well.
For more information about digitizing see our VALOI Guide page.