The Finicky Fooler Hole Cover & Rim is a new concept in hole covers.The key to effectively keep the hole from freezing is to minimize outside air from filtering in, which is difficult to do with conventional hole covers. Constructed of plastic expanded polyethylene, both the hole cover and rim are very durable and flexible. This material will not feze to the ice.Our cover utilizes an insulated rim that is centered over the ice hole, and slush is then packed around the perimeter to provide a seal.The hole cover seats inside the rim, sealing off outside air.The rim provides a 1 perimeter of insulation and the cover provides of insulation. Caneasily be used with an underwater tip-up.