The guards on katanas, known as tsuba, are relatively small compared to the guards on some other types of swords. The size of the tsuba on a katana serves several purposes:

1. Weight and Balance: Katanas are designed to be agile and balanced weapons. The small size of the tsuba helps minimize the weight at the hilt, allowing for better balance and maneuverability. A lighter hilt allows the samurai to wield the katana with greater speed and precision.
2. Hand Protection: While the tsuba on a katana may be small, it still serves the essential function of hand protection. The tsuba provides a barrier between the hand and the blade, preventing the hand from slipping onto the cutting edge during combat. It helps guard against accidental injuries and enhances the safety of the wielder.
3. Versatility and Grip: The small size of the tsuba allows for a more versatile grip on the katana. It enables the samurai to transition between different hand positions and techniques with ease. The reduced size of the tsuba accommodates various grip styles and facilitates rapid changes in grip during combat.
4. Aesthetics and Artistry: The tsuba on a katana is often intricately designed and crafted. It serves as an artistic expression and reflects the skill of the swordsmith. The small size of the tsuba allows for greater attention to detail and intricate designs, contributing to the overall beauty and aesthetic appeal of the katana.

It's important to note that the size and design of the tsuba can vary depending on the specific style, era, and preferences of the swordsmith. While small tsuba are commonly associated with katanas, there can be variations in size and shape based on the individual sword and its intended purpose.