There is provided a fluorine-containing copolymer comprising tetrafluoroethylene unit, hexafluoropropylene unit and a fluoro(alkyl vinyl ether) unit, wherein the copolymer has a content of the hexafluoropropylene unit of 10.4 to 12.0% by mass with respect to the whole of the monomer units, a content of the fluoro(alkyl vinyl ether) unit of 1.3 to 2.9% by mass with respect to the whole of the monomer units, a melt flow rate at 372° C. of 0.7 to 5.0 g/10 min, and the number of functional groups of 70 or less per 10.sup.6 main-chain carbon atoms.

To provide a copolymer capable of forming a coated electrical wire excellent in engine oil resistance, a composition, a molded product, and a coated electrical wire. The copolymer of the present invention is a copolymer comprising units based on ethylene, units based on tetrafluoroethylene, and units based on compound A represented by CH═CX(CF.sub.2).sub.nY (wherein X and Y are each independently a hydrogen atom or a fluorine atom, and n is an integer of from 2 to 6) or compound B represented by CF.sub.2═CF—O—C.sub.3F.sub.7, wherein the crystal lamella thickness determined by the small angle X-ray scattering method is at most 4.0 nm and the melting point is at least 245° C.

There is provided a fluorine-containing copolymer comprising tetrafluoroethylene unit, hexafluoropropylene unit, and a perfluoro(ethyl vinyl ether) unit, wherein the copolymer has a content of the hexafluoropropylene unit of 9.5 to 11.6% by mass with respect to the whole of the monomer units, a content of the perfluoro(ethyl vinyl ether) unit of 1.2 to 2.9% by mass with respect to the whole of the monomer units, a melt flow rate at 372° C. of 19.0 to 28.0 g/10 min, and a total number of —CF.sub.2H, carbonyl group-containing terminal groups, —CF═CF.sub.2 and —CH.sub.2OH of 90 or less per 10.sup.6 main-chain carbon atoms.

There is provided a fluorine-containing copolymer comprising tetrafluoroethylene unit, hexafluoropropylene unit and a perfluoro(propyl vinyl ether) unit, wherein the copolymer has a content of the hexafluoropropylene unit of 9.4 to 10.3% by mass with respect to the whole of the monomer units, a content of the perfluoro(propyl vinyl ether) unit of 1.6 to 2.9% by mass with respect to the whole of the monomer units, and a melt flow rate at 372° C. of 22.0 to 40.0 g/10 min.

There is provided a fluorine-containing copolymer comprising tetrafluoroethylene unit, hexafluoropropylene unit, and a perfluoro(propyl vinyl ether) unit, wherein the copolymer has a content of the hexafluoropropylene unit of 3.55 to 4.10% by mol with respect to the whole of the monomer units, a content of the perfluoro(propyl vinyl ether) unit of 0.39 to 0.90% by mol with respect to the whole of the monomer units, and a melt flow rate at 372° C. of 1.0 to 9.0 g/10 min.

There is provided a fluorine-containing copolymer comprising tetrafluoroethylene unit, hexafluoropropylene unit and a perfluoro(propyl vinyl ether) unit, wherein the copolymer has a content of the hexafluoropropylene unit of 6.0 to 7.6% by mass with respect to the whole of the monomer units, a content of the perfluoro(propyl vinyl ether) unit of 1.5 to 2.4% by mass with respect to the whole of the monomer units, and a melt flow rate at 372° C. of 4.5 to 9.5 g/10 min.

There is provided a fluorine-containing copolymer containing tetrafluoroethylene unit, hexafluoropropylene unit, and a perfluoro(propyl vinyl ether) unit, wherein the copolymer has a content of the hexafluoropropylene unit of 10.3 to 12.0% by mass with respect to the whole of the monomer units, a content of the perfluoro(propyl vinyl ether) unit of 1.6 to 2.9% by mass with respect to the whole of the monomer units, and a melt flow rate at 372° C. of 5.0 to 40.0 g/10 min.

There is provided a copolymer containing tetrafluoroethylene unit and perfluoro(propyl vinyl ether) unit, wherein the copolymer has a content of perfluoro(propyl vinyl ether) unit of 2.14 to 2.75 mol % with respect to the whole of the monomer units, a melt flow rate at 372° C. of 3.0 to 4.2 g/10 min, and the number of functional groups of 20 or less per 10.sup.6 main-chain carbon atoms.

There is provided a fluorine-containing copolymer containing tetrafluoroethylene unit, hexafluoropropylene unit, and perfluoro(propyl vinyl ether) unit, wherein the copolymer has a content of hexafluoropropylene unit of 7.6 to 10.3% by mass with respect to the whole of the monomer units, a content of perfluoro(propyl vinyl ether) unit of 1.3 to 2.9% by mass with respect to the whole of the monomer units, and a melt flow rate at 372° C. of 0.7 g/10 min or higher and lower than 4.5 g/10 min.

There is provided a copolymer containing tetrafluoroethylene unit and perfluoro(propyl vinyl ether) unit, wherein the copolymer has a content of perfluoro(propyl vinyl ether) unit of 3.9 to 5.5% by mass with respect to the whole of the monomer units, a melt flow rate at 372° C. of 2.8 to 4.0 g/10 min, and the number of functional groups of 20 or less per 10.sup.6 main-chain carbon atoms.