Cocoa Mass is the ground cocoa nib (also known as
chocolate liquor). Cocoa Mass contains some cocoa butter because cocoa butter
is part of the cocoa nib naturally. It is usually 1:1 by natural ratio cocoa
butter and cocoa fiber. We do not add cocoa butter to our cocoa mass
as most companies do. Other companies add extra cocoa butter 2:1 to
lessen the impact of the natural cocoa fiber (the dark part of cocoa nibs) bitterness while still
being able to call the cocoa mass 100% (the percentage refers to total
cocoa solids which includes cocoa butter as a solid).
If you only want cocoa fiber with the lowest amount of cocoa butter your best option is cocoa powder. But cocoa powder still contains some butter. Cocoa powder is graded based on the amount of butter in it. 22/24 means the cocoa powder has 22-24% cocoa butter.
I've found our cocoa mass as the best option for all recipes and eating when considering all aspects such as flavor, price and user experience.