These are the go-to cores for EFHW 1:49 type Broadband Transformers or Auto Transformers for 80m-10m End Feed Half Wave (EFHW) Antennas.  Or, 80-10m Common Mode Chokes.
 
Toroidal cores are used in a wide variety of applications such as power input filters, ground- fault interrupters, common- mode filters and in pulse and broadband transformers.
 
 
Dimensions
61.00mm Wide
12.70mm Thick
35.55mm Hole