Best tip up for extreme cold! Frozen over holes can be common when you are using tip ups.  Check out the Trophy Thermal Tip Up from Clam. A thermal foam liner is completely sealed for durability and comes with a  handy tackle compartment that has its own secure spot on the tip up. A bit larger in diameter in size it fits over a 10 inch hole – completely insulates and seals the ice hole.  Rigid high vis green flag for a maximum visual indicator from a distance.