KAGRA is a cryogenic laser interferometer gravitational wave detector under construction in the Kamioka mine in Japan. The detector also incorporates dual-recycled cavity-enhanced Michelson interferometer configuration. The sensitivity of the detector can be improved by the application of signal recycling technic. Moreover, to detect gravitational waves, it is
necessary to isolate the environmental vibrations.
Three signal recycling mirrors of KAGRA will be suspended on Type B suspensions. They incorporate an inverted pendulum vibration isolation table and multiple levels of suspended masses with blade springs for additional horizontal and vertical vibration isolation. Installation is ongoing at the KAGRA site. The design, status and performance of the installed units are described.