What is gsm? The letters 'gsm' stand for Grams per Square Meter, which indicates the overall weight, density and warmth of merino wool and organic cotton fabrics per square meter (which is different to the total weight of the sleeping bag).
Why do we state the gsm? By stating the weight per square meter, we are trying to give you the best indication of how heavy (=warm) or light (=cooler) our SnugBags are.
Why is brushed merino warmer? Our brushed merino fleece involves brushing the fabric on the face side, resulting in a fuzzier, warmer and thicker fabric that is much softer to the touch. The insulation properties of our brushed merino fabric are superior due to its fluffy texture.
Which means that even though the gsm of a 'un-brushed' merino and a 'brushed' merino can be the same (since we are talking about the overall weight per square meter), the brushed merino is always going to be warmer due to its superior insulating properties.