The Classic Modular Armband fits the Galaxy S10 with no case or a thin* case and is the best armband choice if you want the least amount of bulk on your arm while running or working out.
*The Classic M6 Modular Armband for Galaxy S10 fits cases up to 150 x 75 x 10 mm.
Strap Size Arm Size (upper arm circumference)
Small 7 - 9.5 inches (20 - 25 cm) - For THIN arms or wrists only
Medium 10 - 14 inches (25 - 36 cm) - Fits most arms/most common size
Large 13 - 18 inches (33 - 46 cm) - Fits large arms or over clothing
Extender + 4 inches (10 cm)