A solid catalyst component, a method of making the same, a catalyst system incorporating the solid catalyst component, and a method of polymerizing one or more 1-olefins using the catalyst system are disclosed wherein the catalyst component is prepared by contacting, in the presence of an inert liquid hydrocarbon, silica, a soluble organomagnesium compound, an SiCl4 magnesium fixing agent, an alcohol, TiCl4, and a diester compound, followed by extraction with a TiCl4-containing extraction liquid. The inventive catalyst system allows ready control of product molecular weight by control of hydrogen concentration in the reactor, and allows the production of high MI or MF polymers at high productivities.