Are you confused by the random numbers followed by "gsm" you see on many cloth diapering posts/listings (especially when referring to absorbency)? What is GSM and why does it matter?
GSM stands for "Grams per Square Meter" is a measure of density/weight. Generally speaking, the higher the gsm, the more tightly the individual fibers of the material are packed. It does NOT necessarily refer to how thick something is. A 320 gsm piece of terry towel is going to be thicker than a 320 gsm piece of French Terry.
The cloth diaper industry is headed in the right direction as far as companies becoming more transparent about materials, layers, and gsm. It makes it easier for consumers to get a true comparison of products. If company A offers a 3200 gsm bamboo cotton fitted, and company B offers a 4500 gsm bamboo cotton fitted, you can generally expect fitted B to hold more.
If a company does not disclose how many layers, what materials, and what gsm their fabric is, you are certainly entitled to reach out and ask for this information. Failure to disclose this information can mean a few things
1. The company doesn't know their product very well.
2. The company is not educated on the basics of textiles
3. The company is keeping the information to themselves for whatever reason (could be low gsm, poor quality materials, protecting proprietary information etc.)
When GSM DOESN'T matter
Here's the confusing bit. Different textiles behave differently in terms of speed of absorption, and the amount they can hold. So while we can compare the gsm of two pieces of bamboo Terry, you can't really compare cotton to hemp in terms of gsm.
Just for example, a 400 gsm piece of cotton sherpa may hold less than a 300 gsm piece of hemp cotton fleece. This is because hemp is a different fiber and on the whole holds more than cotton. Cotton however absorbs much faster than hemp. You see the problem?
Another area that can be confusing is the textile ZORB. ZORB is specially engineered to be a lighting fast absorber AND hold far more than hemp. However its gsm doesn't always reflect that. So when you are looking at something purely on the basis of gsm, you might (logically) think a 4000 gsm bamboo cotton fitted would hold more than a 2800 gsm ZORB fitted, but you would be wrong.
Hope this helps!