Garmin Training Center software. Waterproof to 1 m. Internal rechargeable battery (10 hr-typical use), 1,000 lap memory, screen size: 1.3" x .8", total size: 2.1" x .7" x 2.7", Weight: 2.7 oz. (77g). Includes: docking cradle, expander strap, A/C charger, PC/USB cable, manuals. 305 Adds: wireless ANT heart rate monitor and monitors pedaling cadence with optional cadence counter.  (less)