In article ,
RubberBiker writes:

K-glass means that the inner pane will have a transparent heat
reflective coating (and stickers on it to show you which face should
be inwards/outwards when fitting it).

K-glass is standard nowadays and the extra cost minimal.

However, it will show if you fit one K-glass pane, and the
others aren't. (It will often show if you replace one too,
as batches/makes are often different tints.)

--
Andrew Gabriel
[email address is not usable -- followup in the newsgroup]