... ,300*300mm,375*375mm,450*450mm material:aluminium 1.One way to four ways airflow.2.Neck sizes are 150*150mm ... ,300*300mm,375*375mm,450*450mm.3.Designed for supply and exhaust of cooled and heated air.4.The centre core is ... coated. Normal colors are RAL 9016/9010. aluminium Square Ceiling air Diffuser air grill