The Humboldt Diamond Grinder is a gravel-ride hosted by Revolution Bicycles and RCMBA. Three routes will be offered this year; Showers Pass 100 miles, Lone Star 70 miles, and Diamond Grinder 23 miles. This is a fundraising event for the Humboldt Composite High School Mountain Bike Team (HCMTB) and RCMBA, two volunteer-only local nonprofits working to improve the local cycling experience.