The STR guard replaces the left-side wheel spacer as its anchor point to the bike. The carbon-fiber semi-circle guard protrudes from between the fork leg and the front brake rotor and is “open” at the end, meaning it doesn’t wrap inward to cover the front of the disc. The guard is larger than the rotor, so it would be very unlikely for something to make contact with the rotor before the guard. This also makes it less likely for mud, rocks, or sticks to get lodged between the guard and the rotor. The leading edge of the guard has a plastic cap that takes the brunt of impacts.