Duo Ortho Deluxe. A firmer feel open coil mattress. The twin spring unit consists of a double-decker 650 system which provides a medium to firm tension. It has a soft, yet hard wearing, Belgian damask cover. Designed to let the mattress breathe, the cover helps to massively reduce the chance of moisture damage. It comes with a 2 year Guarantee. Buy this Duo Ortho Deluxe Now £175.00.