Shimano 15mm Thru x 110mm Rim Brake Bicycle Front Hubs
About Shimano - "Shimano practices good local citizenship, pursues continued access to those areas that are enjoyed by outdoor enthusiasts, and is committed to minimizing our impact on the environment."
This is hub spacing and is the width of the hub. It must match your fork specifications.
This should correspond to the type of brakes you have on the bike.