SupercoilSpring System. Medium – Firm Tension. Hand Tufted. Fibre Fillings.The Ortho Sleep mattress by Airsprung is from the comfortably firm range, it offers firmer support through its supercoil spring system which is an extra heavy 12.5 gauge bonnell spring system that gives the mattress extra support and comfort. The Ortho Sleep mattress has a number of comfort layers which are made from the man made fibre fillings. This is a hand tufted mattress from Airsprung that has a medium to firm tension and is also suitable for a wide range of divan bases, or bedsteads that are available on our website.