This is the lowest published rate we have seen. To qualify for 4.375% you have to pay $1,9995 in fees and 1.67% discount points (Every $100,000 in mortgage equals $1,670 in fees). If your mortgage rates are higher than 6%, it makes sense to refinance as you can easily recoupe back the fee within one or two years.
The rate is only for conforming loans, meaning the loan can’t exceed more than $417,000 and borrowers must high excellent credit scores.