The Galactic supernova remnant (SNR) Vela Jr. (RX J0852.0À4622, G266.6-1.2) shows sharp filamentary structures on its northwestern edge in the hard X-ray band. The filaments are very smooth and located on the extreme outside edge of the remnant. We measured the averaged scale width of the filaments (w u and w d ) with excellent spatial resolution with Chandra, and they are on the order of the size of the point-spread function of Chandra on the upstream side and 49B5 (36B0-88B8) on the downstream side. The spectra of the filaments are very hard and have no linelike structure; they were well reproduced with an absorbed power-law model with À ¼ 2:67 (2.55-2.77) or a SRCUT model with roll ¼ 4:3 (3:4 5:3) ; 10 16 Hz under the assumption of p ¼ 0:3. These results imply that the hard X-rays are synchrotron radiation emitted by accelerated electrons, as mentioned previously. Using a correlation between the function B roll /w 2 d and the SNR age, we estimated the distance and the age of Vela Jr.: the estimated distance and age are 0.33 (0.26-0.50) kpc and 660 (420-1400) yr, respectively. These results are consistent with previous reports, implying that the B-age relation may be a useful tool for estimating the distance and the age of synchrotron X-ray-emitting SNRs. Subject headingg s: acceleration of particles -ISM: individual (G266.6-1.2, RX J0852.0À4622) -supernova remnants -X-rays: ISM