How do I know if my racing guards fit correctly?

Properly fitting racing guards should cover the kneecap completely with the shell centered on the patella when standing. The top edge should reach at least mid-thigh and the bottom edge should extend to the upper shin. When you bend your knee into a deep flexion, the guard should not dig into your thigh or shin, and the kneecap should remain centered under the shell. Straps should be snug enough to prevent any shifting but not so tight that they restrict circulation or cause discomfort.