Zurn® PEX® XL-Low Lead Brass Barb x MPT Adapter. The QQMC_GX adapter is used to transition from female pipe thread to PEX tubing. Manufactured from EcoBrass®,C69300. These fittings, as a system with Zurn® PEX® tube, are pressure rated at 160 psi at 73 deg F, 100 psi at 180 deg F and 80 psi at 200 deg F.