Future colliders (FCC, ESS, CLIC) and high energy accelerators for scientific, industrial and medical applications require high power, high efficiency sources in wide range of frequencies. Novel bunching technology (BAC) together with transverse coupled cavities technology (TCC) allow to achieve efficiency up to 80% and peak output powers till 10 MW in X/C/S bands with long lifetime and low voltage. The bases of BAC method and TCC technology, types of VDBT MBKs in the range of frequencies 1-12 GHz and modulators for them are examined in details with new design/development in range of 3.5MW RF Peak Power X/C/S MBK’s . RF high power systems with the large number of MBKs are considered. Advantages of MBKs in comparison with magnetrons are given.