Arm warmers for running should be selected by matching fabric, fit, and intended use to your weather and training level. Start by considering the climate and your pace: lighter weights for cool mornings, heavier for windy days. Pick a breathable fabric with a comfortable stretch; cotton is soft but holds moisture, while blends like cotton-polyester wick better and dry faster. Decide between a seamless design to reduce chafing and a structured option with compression (like No-Strain) if you need extra support. Finally, check how easy they are to layer with other gear, and pick brands you trust, such as Carina arm sleeves, generic seamless options, or Clue detachable sleeves.