PSL is "Product Specification Level".In case of PSL-1 impact testing is not mandatory and in case of PSL2 impact testing at 0 deg C is mandatory.There is a difference in Chemical composition requirements between PSL1 and PSL2.In case of PSL1 Yield Stress and UTS demands "min" value whereas in case of PSL2 there is a range of "min" and "max" for YS and UTS.