Disclosed are novel hafnium-based metallocene catalyst compounds with the following characteristics: 1) 4,5-dialkyl substitutions on a fluorenyl ligand, and optionally additional substitutions, 2) a cyclopentadienyl ligand, optionally with substitutions, and 3) a bridging group from group 14 of the Periodic Table. Also disclosed are catalyst systems comprising such catalyst compounds and their uses thereof, and polymers produced using such catalyst systems.