My mother, who suffers from rheumatoid arthritis and osteoarthritis, has these on her house-keys and they work really well. Unfortunately, the heads on her car keys are too large for the E-Z Key Turners.One solution I've found is to take an epoxy putty--like J-B Weld or QuikSteel, among others--and shape a new, larger, more ergo head around her slightly oversized keys. The epoxy putty molds like playdough but cures rock hard. The putty can be hand-shaped while still soft or, once cured, cut, drilled, filed, and/or sanded.