The Pebbles do not have a specific “turn off” button. Instead, they're designed to go into an energy-efficient sleep mode when not in use.

1. End your session: After completing your breathing exercise, the Pebbles will naturally end their active mode.
2. Leave the Pebbles inactive: If you simply leave the Pebbles untouched after use, they will automatically go into sleep mode after a period of inactivity. This is an energy-saving condition where the device uses a minimal battery.

Note: If you plan not to use your Pebbles for an extended period of time, it's recommended to keep them in a cool, dry place and maybe charge them occasionally to keep the battery in good condition.