If you have small arms or just want to keep your arms free while running or working out with your Galaxy S21, the Sporteer Zephyr Runner's Belt is the ideal option.
The Zephyr is ultra-thin and lightweight but has plenty of room for your Galaxy S21 (with a case or without a case) and cash, cards, ID, lip balm, or gel shots. A water resistant layer inside the pocket isolates your phone and protects it from sweat, moisture and scratches. And, you'll always have full access to your apps and screen controls through the touch-sensitive screen.
The Zephyr running waist pack fits Galaxy S21 with no case or cases up to 165 x 85 x 12 mm.