A round tip-up for a round hole... why didnt somebody think of it before! The circular shape and insulating design cover the entire hole to prevent freeze-up down to 25 below. Pro-Thermal keeps slush and blowing snow out of the hole, blocks out unnatural light that might spook a shallow water trophy. Each spool shaft is pre-lubed with special "Sub-Zero" lubricant for liquid smooth operation regardless of the temperature. The unique folding spool shaft folds directly into the tip-up base for compact storage.