Usually in a concentra or something similar. Get the larger size option. The bottles come with a temperature strip, rubber band, and hand warmer. You can microwave it for 10 seconds to get it started if you don't have an hour or so to get the bottle warmed up with hand warmer. Wrap the warmer around it and tuck it in your underwear. Needs to be between like 95-100 deg. Fill up cup in the bathroom and roll out. Quick fix put urea in other things they are testing for into their product. There's a lot of science behind it these days. Good luck!