The Classic MX Modular Armband fits the Pixel 3a XL 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 MX Modular Pixel 3a XL Armband fits cases up to 162 x 83 x 10 mm.
If your case is thick and you prefer to keep the case on during your workouts, we recommend the Entropy Modular Armband for Pixel 3a XL.
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)