1. PBT refers to polybutylene terephthalate, one type of polyesters that is being used as fine filament diameter. 2. It refers to the detection assistance to identify the uncleaned zones by means of the toothbrush algorithm. 3. IPX7 means the device can be submerged in water for one meter, for 30 minutes. Splash resistance, water resistance, and dust-proof capacity are not permanent, which may decline with daily wear. 4. The time it takes to charge from 0% to 100%. 5. The average battery life if using twice a day and 2 minutes for each use.