The .7z extension tells us right away that this is a . 7-Zip is known for its high compression ratio, often outperforming standard ZIP or RAR formats. Format: LZMA/LZMA2 compression.
Archives designed to crash your system by expanding into petabytes of data once opened. SSMil-026.7z
If you provide more context on where you found it , I can help you figure out if it's safe or what software you need to view its contents. SSMil-026.7z