  We have performed a metrological characterization of the quantum Hall
resistance in a 1 $\mu$m wide graphene Hall-bar. The longitudinal resistivity
in the center of the $\nu=\pm 2$ quantum Hall plateaus vanishes within the
measurement noise of 20 m$\Omega$ upto 2 $\mu$A. Our results show that the
quantization of these plateaus is within the experimental uncertainty (15 ppm
for 1.5$ \mu$A current) equal to that in conventional semiconductors. The
principal limitation of the present experiments are the relatively high contact
resistances in the quantum Hall regime, leading to a significantly increased
noise across the voltage contacts and a heating of the sample when a high
current is applied.
