December 2024 Purchased on Rakuten Ichiba. Features: The "PBT bristles" used in the TSUYAHAKU brush are characterized by high quality, high heat resistance, and high durability. Compared to the commonly used nylon bristles, PBT bristles have lower water absorption, making them less prone to changes in physical properties and more durable. The bristle tips are 0.02mm (the size that fits between teeth and gums). Bristle hardness: MS (slightly soft)