Recently low attenuation, low bending-loss, broad working-bandwidth, and high damage-threshold hollow core anti-resonant fibers (ARFs) with negative curvature (or hypocycloid) core-surrounds were developed and a variety of cladding structures may prove to be a promisine workbench for many important optical applications ranging from gas-based nonlinear optics, ultra-intense pulse delivery/compression to low-latency data transmission, precise interferometric sensing and quantum optics.