McGee, K.E. Furuta, F. Martinello, M. Melnychuk, O.S. Netepenko, A.V. Wu, G. Xie, Y. JACoW Publishing Geneva, Switzerland 2673-5504 978-3-95450-234-9 10.18429/JACoW-SRF2023-MOPMB024 English 141-144 Contribution to a conference proceedings 2023 2023-09 https://doi.org/10.18429/JACoW-SRF2023-MOPMB024 https://jacow.org/srf2023/papers/mopmb024.pdf Two different vendors supplied the niobium sheet material for PIP-II 5-cell 650 MHz cavities, which was characterized by multiple different ASTM sizes. Cavities subsequently fabricated from these sheets were heat-treated at various temperatures, then the cavities’ flux-expulsion performance was measured. Where the initial measurements of vendor O materials showed that nearly all flux remained trapped despite a high thermal gradient, 900C heat treatment subsequently improved the flux expulsion to an acceptable rate. Understanding and characterizing vendor O materials in this way is key for upcoming and future projects planning to employ niobium sheet from this supplier.