Compatibility: this replacement strap is designed for Fitbit Charge 4/Charge 3/Charge 3 SE. No Charge 3 device included Two Size Available: Small size for 5.5″ – 7.1″ wrist, Large Size for 7.1″ -8.7″ wrist. Size can be adjustable with buckle Premium Waterproof Material: The sport charge 3 strap is made of flexible elastomer material, sweatproof & waterproof, lightweight and easy to dry, great choice for sports No Worry about falling off: The strap for charge 3 with Metal buckle and fastener ring features a stable and reliable performance to keep the wrist band secure Multi Choices: Various colors straps for your charge 3/charge 4, personalize your charge 4 strap to fit different occasion in your daily life