The HKS recirculation fitting will screw into the bottom of the HKS SSQV BOV and allows the discharged air to be rerouted back into the intake stream. This is 1 fitting to recirculate 1 BOV.   Two of these are required for twin turbo applications. 

This will typically improve drivability issues such as bogging and stumbling but will get rid of the BOV atmospheric discharge sound.

This fitting is for a 29mm ID hose.