The wear on disc brake rotors should be regularly checked to ensure safety and performance.The DCA-1 fits most digital, dial, or vernier calipers (including the Park Tool DC-1) and features prominent contact points that allow for measuring the centre of the braking surface, avoiding the unworn edge for accurate measurement.The conical ends of the DCA-1 can be used to measure the centre-to-centre distances of the bolt holes to calculate the BCD of chainrings and cranks.