This item can be found described as LF40 / PC40 thermoscan lenses. Reading through the reviews there seems to be some confusion with regards to the prefix's associated with these lenses i.e. LF40, PC40 , PC20, PC200, PC800 - some turning up in little white boxes and some in the colourful packaging.
The prefix letters only refer to the packaging that the lenses come in and the numbers refer to the quantity, the lenses are Identical, they are made in the USA by KAZ inc, distributed in the UK by Welch Allyn (Ireland) under licence from Braun(they also fit Welch Allyn branded thermometers)
LF's come in the colourfull cardboard packs that hang on the displays in the shops with the picture of the smiling kid on them.
The PC's come in little white boxes of 20 that fit in the slot / holder located inside your braun thermoscan thermometer hard case. They are often sold in bulk packs for use by professionals such as the NHS, doctors, nurserys etc,i believe PC stands for "Packed, cartridge" but I may be wrong there)
PC20 = 1 box of 20 lenses, PC200 = a carton containing 10xPC20 boxes, PC800 = a carton containing 4 x PC200's.
so LF are the same as PC apart from the box.
If You look closely at the product image for LF40 you can see the edge of one of the 2 white PC20 boxes that make up the LF40 pack, So if you order an LF40 pack dont be too put off if you receive 2 x PC20 packs, they are the same thing just without the bit of card with the picture of the baby on
Hope this is of help