Starting out in the cloth nappy world you will notice that you often see - 4, or 5 layer inserts, bamboo terry, bamboo cotton... But it is important to note that this is something which is very important when you are looking at purchasing nappies as it will effect their absorbency.
Generally one 4 or 5 layer insert won't be enough to last your baby from birth the toilet training... Why? Because babies urine output will flucuate over time and they will go through different stages of wetting.
GSM is short for Grams per Square Meter, which essentially will tell you how thick the material is. The higher the GSM, will generally result in a higher capacity insert.
Bamboo terry is a lightweight fabric comprised of bamboo and a small about of polyester for durability which normally ranges between 250 - 320gsm. These are thin but absorbent inserts and are often great as boosters as they won't bulk the nappy out terribly much.
Bamboo/cotton blend inserts are a very popular option for cloth nappy inserts and will generally range from 280 - 500gsm in thickness.
If we break this down further, say you are comparing two 4 layer inserts from different companies where one is 280gsm and the other is 450gsm.... here's some maths:
Insert 1: 4 layers x 280gsm = 1120gsm total
Insert 2: 4 layers x 450gsm = 1800gsm total
That is a big difference and the insert which is 1800gsm will hold 60% more liquid compared to the lighter weight fabric.
This becomes tricky because some companies don't list this information in their product information. Our premium range of inserts are quite high GSM, the bamboo cotton is 450gsm and the hemp/cotton is 400gsm and are all good, absorbent inserts.