There is several silk bedding branded markets in the world, such as California king comforter sets, UK and China. We will mainly talk about UK silk bedding.
In Britain, there are no standards tog rating used for silk duvets. This leaves the market somewhat in turmoil since certain suppliers will suggest one thing, while others may recommend something completely different. The tog rating system is devised by calculating the grams of silk per square meter of fabric.
A duvet that is filled with 250 gsm of silk would be equal to 2-4 togs;
A duvet that is filled with 400 gsm would be equal to 7-9 togs;
A duvet that is filled with 600 gsm would be equal to 10-13 togs.
A lot of suppliers will provide a combination duvet that would be both a 250 and a 400 gsm duvet that connect together. You can often find a good deal or a discount when you buy a combination comforter sets for beds.