Supercoil Spring System. Medium – Firm Tension. Hand Tufted.The Ortho Master by Airsprung is from the comfortably firm range, it offers firmer support and contains the supercoil spring system which is extra heavy 12.5 gauge bonnell spring system which gives added support and firmness. The Ortho Master mattress from Airsprung has a medium to firm tension and is filled with man made fribre fillings for great comfort. Suitable for a wide range of divan bases, or bedsteads that are available on our website. For ease of transport, Airsprung now offer Zip and Link versions of this mattress. In a 5ft the Zip and Link arrives as two 2ft6in mattresses that attach together. The 6ft Zip and Link is two 3ft Mattresses.