I gave these reusable hand warmers a test run today and these are my general impressions:
1. Very hot for 20-mins… Maybe too hot as my hands were sweating
2. Expanded so much I could not comfortably fit my hand in my mitts.
3. Were not producing any heat after 60-minutes
4. Might be best for emergencies, a mid ride warm up, or very short extreemly cold rides.
5. Reusable is very cool.