Thank you for viewing our products. Instant purchase is welcome. Thank you. Simply attach it to your usual pen to record and analyze your study habits. Compatible writing instruments: mechanical pencils, ballpoint pens, stylus pens, etc. *Size guide for compatible writing instruments: diameter 9-13mm *Cannot be attached to regular pencils (diameter 8mm or less) Body weight: Approximately 8g Size: Body: 24 x 30 x 22mm Charging case: 51 x 51 x 35mm Charging method: Body: Charges in the case Charging case: USB charging (USB Type-C) *USB cable not included Battery life: Approximately 7 days (assuming 2 hours of study per day) This product is for use in Japan. It does not support overseas standards.