What are these funny 3 bits with the fresh air feeds

[readiescards]

3 bits of plastic with each feed vent. What for please?

[jack]

They might be for locking the vent at the correct position. I believe they shouldn't be easily adjustable once balanced.

[bpc ventilation]

The plastic fittings are used to direct the airflow away from an area, To use them you need to screw the valve out by approx 80% and slide into the slots on the top of the valve, when commissioning the system you adjust the valve, lock with locknut and fit valve in the desired direction.

Gary

BPC Ventilation