This is the core we use in our mid-power EFHW antennas.  Capable of supporting 300w SSB and 150w of Data and CW.  If you wind the transformer correctly you will get approx. 90% efficiency from a EFHW broad band transformer on 80m-10m bands.

 

Weight: 104 (g)
ID 0.660" Dia (16.76mm)

OD 1.540" Dia (39.12mm)

Length 0.875" (22.23mm)