Uponor Multi-layer Componsite (MLC) (formerly MultiCor) is a multi-layered composite tubing consisting of an interior aluminum pipe lined with inner and out layers of PEX (commonly referred to as PEX-al-PEX). Uponor MLC offers 100% oxygen diffusion and can be embedded in concrete or installed in walls, floors and ceilings. One of the best qualities of Uponor MLC tubing is that once is is shaped in a certain way, it will hold that shape. Uponor MLC tubing meets ASTM F1281 and is listed to NSF. The tubing is rated by the PPI for 200°F at 100 psi, 180°F at 125 psi, 140°F at 160 psi and 73.4°F at 200 psi.