How many grams is a fleece?

hi ive wondered this myself! i actually went to buy a 100gms combo for my little pony today because hes currently in a fleece under his lightweight and the girl in the tack shop who is quite sensible and has worked there a very long time said the fleece and lightweight would be closer to 180gms .
 
Lol obviously, but your average fleece - is is as warm as a 100g rug or warmer or not so warm? I don't own a 100g to do the experimenting! My reason for asking is wondering if I should purchase a 100g or similar weight. But if fleece is around that then I won't bother!
 
I'd say the (cheap?) single thickness polar fleece type rugs are about the same warmth as a cotton summer sheet, but the super thick horsewear striped fleeces are about the same as the weatherbeeta 100g stable rugs.
 
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