Abel/Ross on-line marketing posts line backing capacities for presently mfr'd reels and there is a pdf file online for their discontinued models, but neither of these state whether the amount of 20# backing is based upon WF or DT lines. So I called. WF. I guess they don't bother to make that clear because they believe WF is the norm or maybe it's because WF permits more backing and they believe that's desirable. Anyway, that's the answer.