Recent product development has focussed on developing a range of higher strength structural grades, covering the strip thickness range 0.9-1.5 mm, utilising Nb microalloying. A wide range of Nb levels have been successfully strip cast by the CASTRIP® process. Niobium was found to retard austenite grain refinement and substantially enhanced hardenability, which produced significant microstructural hardening and higher strength hot band. Niobium was retained in solid solution enabling further significant strengthening to be achieved from an age hardening heat treatment. Strength levels ranging from 400 MPa to in excess of 550 MPa, in combination with high ductility, were achieved in the age hardened and hot dip galvanised condition, utilising the annealing furnaces of a conventional hot dip galvanising line. The effect of microalloying content and processing conditions on the microstructure and final mechanical properties of Nb microalloyed UCS products produced by the CASTRIP process are described.