Official websites use .gov
A
.gov website belongs to an official
government organization in the United States.
Secure .gov websites use HTTPS
A lock (
) or https:// means you've safely
connected to the .gov website. Share sensitive
information only on official, secure websites.
The midpoint hole diameter used for the WHOPES category weight is indicated by an orange dashed vertical line. The median hole diameter in each category is indicated by a green dotted vertical line.
