AUKTools Dust Extraction Blast Gate 100mm (4″) Diameter - WR-DUSGATE4

The AUKTools Dust Extraction Blast Gate - 4" OD fitting let you “turn-off” the suction from your dust collector to use other machines connected to other branches of your system. Tapered port each side of the sliding gate fits inside most 4” dust collection hose.

eBay