  There exists significant in-plane anisotropy between $a$ and $b$ axis for
various properties in YBCO. However recent thermal conductivity measurement by
Chiao et al. which confirms previous microwave conductivity measurement by
Zhang et al., shows no obvious anisotropy in the context of universal
transport. We give a possible explanation of why the anisotropy is seen in most
properties but not seen in the universal transport.
