Ressi PFS 620 Ressi PFS 620 is a premix pourable low slump floor screed which is highly suitable for commercial & residential use. Ressi PFS 620 is suitable for both old and new, internal, and external floorings. The application thickness of Ressi PFS 620 is between 25mm to 75mm. Ressi PFS 620 is an ideal material to be used as a floor screed for exposed roof tops, a bed prior to carpeting and laying tiles etc.