3K refers to the type of cosmetic weave that you see on the exterior of the frame or component.

The only differences between a 12k weave and a 1k weave is how much they cost, how much they weigh and what they look like.

The lower the number, the smaller the weave pattern and the lighter/more expensive the material is.

What you are trying to get into is the type of structural carbon fibre that is used in the frame.