Copolymer, injection molded body, member to be compressed, and covered wire

A copolymer, comprising tetrafluoroethylene unit and a perfluoro (propyl vinyl ether) unit,

• wherein the copolymer has a content of the perfluoro (propyl vinyl ether) unit of 2.8 to 3.5% by mass with respect to the whole of the monomer units, a melt flow rate measured at 372° C. under a 5 kg load in accordance with ASTM D1238 of 31 to 38 g/10 min, and a total number of functional groups of —CF═CF2, —CF2H, —COF, —COOH, —COOCH3, —CONH2 and —CH2OH is 50 or less per 106 main-chain carbon atoms,
• wherein the copolymer optionally comprises a monomer unit originated from a monomer copolymerizable with the tetrafluoroethylene unit and the perfluoro (propyl vinyl ether) unit, and
• the copolymer has a content of the monomer unit of up to 0.7% by mass with respect to the whole of the monomer units.