The stricter regulations regarding the sealing of air ducts ( most recently raised to level D sealing ) has resulted in further reasearch and development into the construction of sealing rings. HITAC-D is the most secure system on the market today, with a test result that was 50% under the allowed leakage factor for level D sealing ( according to the Swedish testing and research institute ). Our method of treating the rubber sealing rings result in the highest degree of sealing without any friction. open catalog >>