Never used Garmin HRM Dual General Specifications MODULE DIMENSIONS (LXWXD): 2.4" W x 1.3" H x 0.4" D (62 mm x 34 mm x 11 mm) SIZE RANGE: -Strap Length: 25"–38.5" (63.5–98 cm) -Fits chest size: 26.5"–52" (67.5–132 cm) WEIGHT: 1.9 oz (54.4 g) WATER RATING: 1 ATM BATTERY TYPE: CR2032 BATTERY LIFE: Up to 3.5 years (using 1 hour per day)