Yes. An adult can meaningfully increase clubhead speed while training with a Junior length Stack. If your driver length is 42" or shorter, then a Junior length will work best. The main consideration is the length of your driver.  The Stack System is primarily concerned with increasing your clubhead speed with your driver. As such, we want to provide overload and overspeed stimuli relative to your driver. If your driver length is  between 42" and 44", then either length Stack will be equally effective.  If your driver length is greater than 44", we recommend using an Adult length Stack. This is regardless of your age, height, or swing speed.The Junior length Stack is ~3" shorter than the Adult version, which makes it a viable option for folks training in a confined space with lower ceilings.Please make sure you correctly complete the Profile information section in the app.  The algorithms for the Junior length stack are meaningfully different from the Adult version to ensure that correct overspeed and overload conditions are met.