The amount of Thinsulate you need for ice fishing boots depends on the type and style of boot, as well as the temperature outside. Generally speaking, a minimum of 200 grams is recommended for temperatures below -20°C. For colder temperatures, 400-600 grams may be necessary to keep your feet warm and comfortable while out on the ice. It's important to remember that too much insulation can make your feet sweat, so it's best to find a balance between warmth and breathability when selecting your boots.