Mattresses with wired core are made of handmade conical springs (narrow in the middle than at the ends), which are joined by a spiral wire. The springs are specially threated so they can stay permanently elastic and resistant to breaking. Thanks to progressive force of the spring, wired „bonnell“ core collapses softly at first and harder with more load. This is classic and most famous system of spring wired cores which makes these mattress very reliable and economic. Comfor for these mattresses is provided by layers of silicon PES cotton wool, PU, HR or memory foam. Covers can be: unremovable from „žakard“ linen or removable and washable from double jersey linen (Aloe Vera, Bamboo, Tencel).