For use in baluns and line-isolators. More than enough for UK legal power so perfect for your QRO balun project. 8 turns of RG58/RG316 (400w SSB) or RG142 (1kW CW/Digi) make a great "resistive" balun/choke for 7-30MHz. If you operate on 160m, 80m or 60m, consider using an FT240-31 for increased choking impedance.
Toroid sizes/types are easy to ID, the "240" translates to 2.4" (size) and the "43" is the ferrite mixture. What type do you need? 43 is good from 7MHz and up (and a good general-purpose 7-30MHz solution) while 31 is good for lower HF bands. Remember, you can stack the cores for increased choking and power-handling. As always, ratings need to factor in the aerial (SWR) match and duty-cycle.