The London Interbank Offered Rate (LIBOR) is a benchmark rate that helped inform interest rates on ARMs, among other financial products. Due to limitations that made it unreliable, LIBOR is phasing out and being replaced by the Secured Overnight Financing Rate (SOFR). The difference: With LIBOR ARMs, the adjustment to the rate occurs once per year. With a SOFR ARM, that change takes place every six months. Many banks ceased originating products tied to LIBOR at the end of 2021, but you might still see some LIBOR ARMs advertised on Bankrate for the time being.