They are a rebranded name for Aussie Locker, I bought a Front locker and was so impressed I bought a rear, have run them in YJ/XJ and TJ, sometimes just the front; there is a gnarly rocky lane near my house and with just the front locker in the TJ climbed up at 1200 revs with no slip or spin.
They are awesome,
check your front UJ's though as of course they will be under more stress, I carry a spare pair of shafts when competing. If your driving style is nail it then I wouldn't recommend lockers imho.
The lockers give so much more control that you can slowly through/over stuff and therefore much less stress on the Jeep, contents and the terrain.
I Think they have a free delivery to the UK.