A barrier structure selected from bottles, tanks, containers, pipes, recipients and films comprising at least one fuel barrier layer comprising a MPMDT/XT copolyamide wherein: MPMDT is a unit with amide motif present at a molar level going from 5 to 50%, in particular from 5 to 45%, preferably from 15 to 45%, more preferentially from 20 to 45% where MPMD represents 2-methyl pentamethylene diamine (MPMD) and T the terephthalic acid, XT is a unit with majority amide motif present at a molar level ranging from 50 to 95%, in particular from 55 to 95%, preferably from 55 to 85%, more preferentially from 55 to 80%, where X is a C9 to C18 linear aliphatic diamine, preferably C9, C10, C11 and C12, and where T is the terephthalic acid, said copolyamide having a melting temperature: 250°C <T m ≤ 300°C such as determined according to ISO 11357-3 standard, - in the MPMDT and/or XT units, independently of each other, up to 30% by mole, relative to the total quantity of the carboxylic diacids, the terephthalic acid may be replaced by other aromatic, aliphatic or cycloaliphatic carboxylic acids comprising 6 to 36 carbon atoms, in particular 6 to 14 carbon atoms, and - in the MPMDT and/or XT units, independently of each other, up to 30% by mole of the MPMD and/or according to the case of X, relative to the total quantity of diamines, may be replaced by other diamines comprising from 4 to 36 carbon atoms, in particular 6 to 12 carbon atoms, and - in the copolyamide, not more than 30% by mole, relative to the total quantity of the monomers, may be formed by lactams or aminocarboxylic acids, and - provided that the sum of the monomers which replace the terephthalic acid, the MPMD and X does not exceed a 30% by mole concentration relative to the total quantity of the monomers used in the copolyamide, and - provided that the MPMD is not completely substituted, said structure being devoid of reinforcing fibers, and in which a second layer is present, layers and being susceptible to adhere to each other, said layer comprising at least one polyamide selected from an aliphatic polyamide and an aromatic polyamide, in particular an aliphatic polyamide, and said barrier layer is in contact with the fluid. XT is a unit with majority amide motif present at a molar level ranging from 50 to 95%, in particular from 55 to 95%, preferably from 55 to 85%, more preferentially from 55 to 80%, where X is a C9 to C18 linear aliphatic diamine, preferably C9, C10, C11 and C12, and where T is the terephthalic acid, said copolyamide having a melting temperature: 250°C <T m ≤ 300°C such as determined according to ISO 11357-3 standard, - in the MPMDT and/or XT units, independently of each other, up to 30% by mole, relative to the total quantity of the carboxylic diacids, the terephthalic acid may be replaced by other aromatic, aliphatic or cycloaliphatic carboxylic acids comprising 6 to 36 carbon atoms, in particular 6 to 14 carbon atoms, and - in the MPMDT and/or XT units, independently of each other, up to 30% by mole of the MPMD and/or according to the case of X, relative to the total quantity of diamines, may be replaced by other diamines comprising from 4 to 36 carbon atoms, in particular 6 to 12 carbon atoms, and - in the copolyamide, not more than 30% by mole, relative to the total quantity of the monomers, may be formed by lactams or aminocarboxylic acids, and - provided that the sum of the monomers which replace the terephthalic acid, the MPMD and X does not exceed a 30% by mole concentration relative to the total quantity of the monomers used in the copolyamide, and - provided that the MPMD is not completely substituted, - in the MPMDT and/or XT units, independently of each other, up to 30% by mole, relative to the total quantity of the carboxylic diacids, the terephthalic acid may be replaced by other aromatic, aliphatic or cycloaliphatic carboxylic acids comprising 6 to 36 carbon atoms, in particular 6 to 14 carbon atoms, and - in the MPMDT and/or XT units, independently of each other, up to 30% by mole of the MPMD and/or according to the case of X, relative to the total quantity of diamines, may be replaced by other diamines comprising from 4 to 36 carbon atoms, in particular 6 to 12 carbon atoms, and - in the copolyamide, not more than 30% by mole, relative to the total quantity of the monomers, may be formed by lactams or aminocarboxylic acids, and - provided that the sum of the monomers which replace the terephthalic acid, the MPMD and X does not exceed a 30% by mole concentration relative to the total quantity of the monomers used in the copolyamide, and - provided that the MPMD is not completely substituted, said structure being devoid of reinforcing fibers, and in which a second layer is present, layers and being susceptible to adhere to each other, said layer comprising at least one polyamide selected from an aliphatic polyamide and an aromatic polyamide, in particular an aliphatic polyamide, and said barrier layer is in contact with the fluid.