A hunting boot with 200g of insulation is perfect for mildly cold days or evenings with a high activity level.
400g of insulation will work for mildly cooler days with moderate or little activity.
A boot with 800g of insulation is perfect for cold days between 30 and 40 degrees with light activity.
1200-2000g of insulation is suitable for icy weather where there is little or no activity. However, these boots are thick and not as easy to move around in.