Beaver Dam Round Tip-Up Original Beaver Dam Assembly; Production quality line guide, block and spool Wood Laminate Base; Exterior grade treated plywood sealed to withstand the most extreme outdoor conditions Extendable Flag Spring; 16 - inch extendable flag with super soft spring for maximum sensitivity Insulating rubber back; Hi-grad insulated, slip resistant rubber bottom to minimize hole freeze Line guide; Precision molded line guide swings into the direction of the strike, yet prevents line bait unwinding