Shimano 15mm Thru x 100mm 36 hole 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.
The hub drilling is the number of spoke holes. It must match your rim spoke count.