  Radio relics are diffuse synchrotron sources in galaxy clusters that are
believed to trace large-scale shock waves. We have discovered a new double
radio relic system in PSZ1 G096.89+24.17 (z=0.3) and have carried out a
full-polarization radio observation using the Westerbork Synthesis Radio
Telescope (WSRT) at 1.4 GHz. The observation revealed the presence of two
relics located on the two diametrically opposite sides of the cluster and hints
of a central radio halo. The linear sizes of the relics are $\sim 0.9$ and
$\sim 1.4$ Mpc.
  We carried out an analysis of all known double radio relics by using radio,
X-ray and Sunyaev-Zeldovich (SZ) data. We find that the radio luminosity of
double relics is a steep function of the cluster mass, with $L_R \propto
M^{2.83\pm0.39}$. If we include single radio relics, this relation is
maintained. This dependence has implications for the origin of magnetic fields
at the relic's locations.
