[UK-CONTEST] Ferromagnetics Choke Baluns

[MM0BQI]

Hi 
I have two of the above but can find nothing on the web about them other than I believe they were made by a Welsh company.
They are approx 11 inches by one inch, white plastic tubes with 'Ferromagnetics Choke' written on them.
Both have an SO239 sockets at one end.  At the other end one has a short pigtail of RG58 to a PL259 and the other has two screw terminals (possibly for a dipole)
Does anyone have any info on them, frequency range/ power etc?
Possibly looking to use them on a topband inverted L and HF2V for 40/80.
Thanks
Jim
MM0BQI