In message , Arthur51
writes
I've read a few posts from the past here and people have talked of
14mm upto 22m thick options.

Or even upto 28mm nowadays.


What are the advantages/disadavatages of thin against thicker
double glazed units?


Thicker gives better heat and sound insulation.

Thinner needs a shallower rebate and maybe a little cheaper?

The units I want are for my timber front door frame..sidelights and top
light
to be fitted into 45mm x 20mm deep rebates.

Presumably an old single glazed frame? Even 14mm would be pushing it
-you need to allow a bit for bedding it against the frame, and enough
space for the bading which normally holds the units in place.
--
Chris French