In article ,
WM writes:
Here in the UK, at my local Tesco supermarket I saw some GLS bulbs
which has a glass envelope that were slightly smaller than usual.

What's the idea behind this?

I don't know. Philips have started making theirs smaller.
These smaller GLS lamps won't fit into a number of fittings
my parents have because the neck is too short.

I wonder if GLS lamp sizes are covered by a British or EU
statndard?

Wouldn't a 100W filament make a smaller bulb glass envelope get
hotter than the larger standard envelope.

And therefore wouldn't this make the life shorter?

There are loads of factors which affect lamp life.

--
Andrew Gabriel