A Fair-Rite larger mix 2.9" mix 43 core suitable for high power EFHW and EFRW when stacked, or as a high-power common mode choke.
 
If you are looking for a high-power end fed half wave antennas for 160m-40m this is the go-to core.  Stack 3 cores for 1kw+.
 
This core is also suitable for use in high power radio amateur common mode chokes.  Used with Teflon coax like RG142 you will be ok at legal UK limits.