In conclusion, the recent progress of ULMA ChG PCFs shows promise for high-power mid-IR applications at 100 W. Single modes and low bending loss are traded off in ultra-low-NA ULMA ChG PCFs. Finally, it is pointed out that refractive index fluctuation at the order of 10^-5 in the ChG glasses (Fig. 9) is the ultimate barrier responsible for i) increasing the MFD of a ULMA ChG PCF to 200-μm or higher, and ii) mode instability of such a ULMA PCF during high-power operation. To address such a technical issue, additional glass purification and precise thermal management are proposed.