Fiberglass is the workhorse of all the fabrics. It is cheap and readily available. Its a common material to use in mold making, and too keep costs down it can sometimes provide thickness to a carbon part.
It is also the ‘stretchiest’ fabric we sell! Yes glass stretches! What this means for your parts is that they will not be as rigid or light compared to using a carbon fabric which does not like to stretch. However this feature can be useful if your needing the part to flex, or even make a spring!