katones - you use them over fitted nappies (ie non- PUL covered nappy) they heap to absorb and evapourate the wee to kep bub dry (esp over night).

FLongies are fleece ones - FionaJill makes them
Wool longies are wool .. obviously

i started to use them as i found my BBH wool covers did not have a high enuf rise over the BBB to stop wicking/leaks when DD slept on her belly