A composition, which is a curable comprising: - a perfluoro(poly)ether group-containing silane compound which is a compound having two or more Si atoms each bonding to at least one group selected from OH and a hydrolyzable group, and a perfluoro(poly)ether group, wherein the Si atom bonding to at least one group selected from OH and a hydrolyzable group is present at each of both ends of a molecular backbone of the perfluoro(poly)ether group-containing silane compound, and the perfluoro(poly)ether group is a group of the formula: -(OC 6 F 12) a -(OC 5 F 10) b -(OC 4 F 8) c -(OC 3 X 10 6) d -(OC 2 F 4) e -(OCF 2) f - wherein a-d each independently are an integer of 0-30, e and f each independently are an integer of 1-200, (a+b+c+d+e+f) is ≥ 5, the order of the repeating units in parentheses with the subscript a, b, c, d, e or f is not limited, the ratio e/f is < 1.0, and X 10 each independently is H, F or Cl; - an organosilicon compound selected from: an organosilicon compound of any of the formulae -: (R g3 -O) ε2 -Si-R g4 4-ε2 ··· wherein, each independently at each occurrence, R g1 is an optionally substituted monovalent C 1-8 -hydrocarbon group; R g2 is an optionally substituted divalent C 1-20 -hydrocarbon group; R g3 is H or a monovalent organic group; R g4 is an unsubstituted monovalent hydrocarbon group having 1 to 12 carbon atoms; R g6 is R g8 -R g7 -; R g7 is a single bond, -O- or a divalent organic group; R g8 is amino, epoxy, a methacrylic group, vinyl or mercapto; ε1 is an integer of ≥ 1; ε2 is 2 or 3; ε3 is 2 or 3; ε4 is an integer of ≥ 2; ε5 is 1 or 2; and ε6 is an integer of ≥ 0, and tetraethoxysilane, tetramethoxysilane, methyltriethoxysilane, methyltrimethoxysilane, dimethyldimethoxysilane, aminopropyltriethoxysilane, aminopropyltrimethoxysilane, tridecafluoro-n-octyltriethoxysilane and tridecafluoro-n-octyltrimethoxysilane; and - a catalyst, wherein the composition comprises 0.1-30 parts by mass (pbm) of the organosilicon compound per 100 parts by mass (pbm) of the perfluoro(poly)ether group-containing silane compound. - a perfluoro(poly)ether group-containing silane compound which is a compound having two or more Si atoms each bonding to at least one group selected from OH and a hydrolyzable group, and a perfluoro(poly)ether group, wherein the Si atom bonding to at least one group selected from OH and a hydrolyzable group is present at each of both ends of a molecular backbone of the perfluoro(poly)ether group-containing silane compound, and the perfluoro(poly)ether group is a group of the formula: -(OC 6 F 12) a -(OC 5 F 10) b -(OC 4 F 8) c -(OC 3 X 10 6) d -(OC 2 F 4) e -(OCF 2) f - wherein a-d each independently are an integer of 0-30, e and f each independently are an integer of 1-200, (a+b+c+d+e+f) is ≥ 5, the order of the repeating units in parentheses with the subscript a, b, c, d, e or f is not limited, the ratio e/f is < 1.0, and X 10 each independently is H, F or Cl; the Si atom bonding to at least one group selected from OH and a hydrolyzable group is present at each of both ends of a molecular backbone of the perfluoro(poly)ether group-containing silane compound, and the perfluoro(poly)ether group is a group of the formula: -(OC 6 F 12) a -(OC 5 F 10) b -(OC 4 F 8) c -(OC 3 X 10 6) d -(OC 2 F 4) e -(OCF 2) f - wherein a-d each independently are an integer of 0-30, e and f each independently are an integer of 1-200, (a+b+c+d+e+f) is ≥ 5, the order of the repeating units in parentheses with the subscript a, b, c, d, e or f is not limited, the ratio e/f is < 1.0, and X 10 each independently is H, F or Cl; - an organosilicon compound selected from: an organosilicon compound of any of the formulae -: (R g3 -O) ε2 -Si-R g4 4-ε2 ··· wherein, each independently at each occurrence, R g1 is an optionally substituted monovalent C 1-8 -hydrocarbon group; R g2 is an optionally substituted divalent C 1-20 -hydrocarbon group; R g3 is H or a monovalent organic group; R g4 is an unsubstituted monovalent hydrocarbon group having 1 to 12 carbon atoms; R g6 is R g8 -R g7 -; R g7 is a single bond, -O- or a divalent organic group; R g8 is amino, epoxy, a methacrylic group, vinyl or mercapto; ε1 is an integer of ≥ 1; ε2 is 2 or 3; ε3 is 2 or 3; ε4 is an integer of ≥ 2; ε5 is 1 or 2; and ε6 is an integer of ≥ 0, and tetraethoxysilane, tetramethoxysilane, methyltriethoxysilane, methyltrimethoxysilane, dimethyldimethoxysilane, aminopropyltriethoxysilane, aminopropyltrimethoxysilane, tridecafluoro-n-octyltriethoxysilane and tridecafluoro-n-octyltrimethoxysilane; and R g1 is an optionally substituted monovalent C 1-8 -hydrocarbon group; R g2 is an optionally substituted divalent C 1-20 -hydrocarbon group; R g3 is H or a monovalent organic group; R g4 is an unsubstituted monovalent hydrocarbon group having 1 to 12 carbon atoms; R g6 is R g8 -R g7 -; R g7 is a single bond, -O- or a divalent organic group; R g8 is amino, epoxy, a methacrylic group, vinyl or mercapto; R g7 is a single bond, -O- or a divalent organic group; R g8 is amino, epoxy, a methacrylic group, vinyl or mercapto; ε1 is an integer of ≥ 1; ε2 is 2 or 3; ε3 is 2 or 3; ε4 is an integer of ≥ 2; ε5 is 1 or 2; and ε6 is an integer of ≥ 0, and tetraethoxysilane, tetramethoxysilane, methyltriethoxysilane, methyltrimethoxysilane, dimethyldimethoxysilane, aminopropyltriethoxysilane, aminopropyltrimethoxysilane, tridecafluoro-n-octyltriethoxysilane and tridecafluoro-n-octyltrimethoxysilane; and - a catalyst,