The Apple Watch Solo Loop 40mm Band – Ultramarine (MAY74AM/A) Size 4 is a sleek, stretchable band designed by Apple Inc. for compatible Apple Watch models, made from soft liquid silicone rubber that provides a smooth and lightweight feel on the wrist while being durable, sweat-resistant, and swim-proof; its unique single-piece design has no clasps or buckles, allowing the band to stretch easily over the wrist for a secure and comfortable fit, while the Ultramarine color gives a modern and stylish look suitable for everyday wear, workouts, and casual or professional use.