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We create a reconfigurable transmission cavity though cascading two adjacent waveguide-bends, where the released energies are shown to possess different transmission bandwidths when the C-slit meta-gates are inserted into the bending corners with different rotating angles. A circuit modelling is proposed for the analysis of such a waveguide-bend cavity and perfectly accounts for all the details of the transmission spectrums, including the meta-gated transmissions and also the spurious passbands. Finally, we fabricate and test the waveguide-bend cavity, and the transmissions are shown to be reconfigured from original multiple passbands of bare cavity to the single tunable filtering transmission with the C-slit meta-gates in the experiment.