Here's a breakdown of factors to consider:
* Service Quality: If you're happy with the service, the technician was professional, and the results are good, tip towards the higher end of the range (20%). If the service was just okay, 15% is appropriate.
* Complexity/Time: If the hair removal was more extensive, took a long time, or was particularly challenging, you might consider tipping closer to 20%.
* Your Budget: Tip what you are comfortable with.
Ultimately, the amount you tip is at your discretion based on your experience.