Gentle but not great.
The GK shampoo and conditioner seem to work well together.  The combination is gentle, but doesn’t seem to add enough moisturizing to use  on it’s own or to counteract the drying of the GK leave in conditioner.  Other than this combination, GK products don’t seem to work well with each other, nor with any of the other products I have tried.  GK products are not cheap, but their results are disappointing ☹️
Rating: 2 stars