101 copper, also known as OFE or OFHC copper, is made up of 99.99% copper. It is a commercially pure high conductivity grade of copper that has no oxygen, giving it excellent electrical and thermal conductivity. The lack of oxygen gives 101 immunity to hydrogen embrittlement at elevated temperatures. It is excellent for hot working, cold working, and forging. 101 can also be soldered, brazed, and welded easily. It's typically used in conductors and particle accelerators.