Excellent product - I purchased the 810nm version which has been beneficial for my mood and I believe has supported my general brain health. It's great to have the pulsing available at both 10Hz (Alpha waves) and 40Hz (Gamma waves), in line with the latest scientific research around transcranial photobiomodulation. It does run quite warm to the touch on extended runtimes but this is to be expected for a product without active heat dissipation and Kinreen have advised me that the product is FDA approved and completely safe. Overall the hat is well constructed and the buttons have a pleasant and durable quality to them. The zipper at the back allows for adjustable for larger heads such as my own and ability to use the hat in different configurations for better head (brain) surface area coverage. I look forward to working more with Kinreen in the future, they have exceeded my expectations in both product and service.