The Arm Sleeve Accessory is designed specifically for the Whoop 4.0 model, making it a perfect fit for those who engage in running and jogging activities. Made of durable nylon material, the black arm sleeve is lightweight and includes an optical sensor for accurate monitoring. It is compatible with smartphones and comes with a 30-day warranty for added peace of mind. The unisex size and standard dimensions make it a versatile accessory for fitness enthusiasts looking to track their performance and improve their workouts.