In BJJ the belts, through the different colors, serve as an indicator of the level of knowledge of the fighter's art; having white, blue, purple, brown and black, in that order from beginner to more advanced.
Like the Kimono they are made of reinforced cotton since they need to be made of a material resistant to the grips and struggles to which they will be subjected during combat.
With regard to sizes, in men they are designated by the letter A, starting from A0 to A5. In women they are designated by the letters F or W, and also range from 0 to 5. Children's sizes usually range from M0000 to M4