CORE Springbox System. This model is designed for users who prefer pocket springs with a slightly firmer core. FABRICS AND PADDING High-density stretch fabric with antibacterial and anti-mite treatment. Quilted with state-of-the-art technology using a layer-to-layer system. INTERIOR The interior of the Perla model combines the adaptability of Viscodensitv with the comfort and breathability of Oxicore and Fibersoft. FINISHING Hand-stitched side handles