Y Branch enable you to construct double runs and use multiple machines hookups. 

Having a smooth inner surface and there is no obstruction to the airflow.

Also,these are available in a range of sizes to suit the duct and machine extraction outlet. 

DCS-Y150-2X100 Y BRANCH FROM 150MM TO 2X100MM, ROLLED EDGES ON BOTH ENDS

DCS-Y180-2X125 Y BRANCH FROM 180MM TO 2X125MM, ROLLED EDGES ON BOTH ENDS

DCS-Y200-2X150 Y BRANCH FROM 200MM TO 2X150MM, ROLLED EDGES ON BOTH ENDS