3K, 12K, 18K carbon: what it means in padel

The K figure indicates how many thousand filaments make up each carbon fibre tow used in the face: 3K means 3,000 filaments.

The number changes the weave of the fabric and the feel, but on its own it doesn't tell you whether a racket is stiffer or more powerful: resin, number of layers and core matter too. In general, carbon faces are stiffer and more precise than fiberglass ones.