Compatibility: -Compatible with Fitbit Ace 3 activity tracker -Material: -Silicone. TPU -Size: -Fits wrists from 5.1-8.7 inches -Made of high quality soft silicone material, comfortable and durable. Prevents skin irritation for kids and protects the Ace 3 tracker from dust and scratches. Safe for swimming, running, dancing or working out. Multiple colors for your choice. Strap is suitable for boys, girls, and children. Size can be adjusted to fit individual wrists. Strap fits wrists from 5.1"-8.5" inches. Environmentally friendly and breathable, sturdy and durable, very comfortable to wear. Easy to install and remove, not easy to fall off. Plastic buckles hold the device well. With them, you can enjoy your sports activities.