The Apple Watch Sport Loop band is woven from nylon thread to create a hook-and-loop closure. They were available for the 38/40 mm and 42/44 mm Apple Watch models, and fit 130–200 mm wrists (40 mm) and 145–200mm wrists (44 mm).
The Apple Watch Sport Loop band has been available in several styles. The 2019 designs were comprised of a base color and one or more accent colors. In this Cerulean example, the edges and plastics are light blue, and the inside pattern is comprised of threads in light blue, royal blue, light orange, and white.
Apple describes the Apple Watch Sport Loop band:
“Soft, breathable, and lightweight, the Sport Loop features a hook-and-loop fastener for quick and easy adjustment. The double-layer nylon weave has dense loops on the skin side that provide soft cushioning while allowing moisture to escape. On the reverse side, the attachment loops are securely anchored for superior durability.”