it works exactly as advertised but you MUST pay close attention to the temp as a single heater will raise the temperature well past 100 if left on the vial for more than 15 minutes, even when us...
Moreing room temp water, and as you generally are timed as to how long you can be in the bathroom its very important to wait as long as you can before applying the heater because you may not have enough time to cool the vial back below 100. Again, great product, but i recommend getting an extra warmer and practice, practice, practice. Good luck!