Both the Magnesium Soak and the Hot Mustard Soak come in a packet with 5 pre-packed sachets in each. If you are not sure how your body will feel, then start by putting half a sachet in the bath, if that feels ok then use the full sachet from then on. If you want to use the Magnesium Soak and Hot Mustard Soak together, start by trying a half a sachet of each in the bath, if you like the effects, you can use a full sachet of each in a bath. For the best benefits the bath water should be nice and relaxing hot, but not boiling hot.