A compound which is a perfluoro(poly)ether group containing silane compound of the formula: XR a α Ri b β R c γ wherein, all each independently at each occurrence: X is a 3-10 valent organic group; R a is Rf-PFPE-; Rf is C 1-16 -alkyl optionally substituted by one or more F atoms, and preferably is C 1-16 -perfluoroalkyl; PFPE is a group of the formula: -(OC 4 F 8) a -(OC 3 F 6) b -(OC 2 F 4) c -(OCF 2) d - wherein a, b, c and d are each independently an integer of 0-200, ( a + b + c + d) ≥ 1, and the occurrence order of the respective repeating units in parentheses with the subscript a, b, c or d is not limited in the formula; R b is -Z-SiR 1 k R 2 l R 3 m; Z is O or a divalent organic group; R 1 is R b ' which is defined as R b; R 2 is OH or a hydrolyzable group; R 3 is H or lower alkyl; k is an integer of 0-3; l is an integer of 0-3; m is an integer of 0-3; in R b the number of Si atoms which are straightly linked via the Z group is ≤ 5, in one R b ( k+l+m) = 3, and in formula at least one l is ≥ 1; R c is a radical scavenger group or an ultraviolet ray absorbing group, wherein the radical scavenger group includes a residue of benzophenones, benzotriazoles, benzoic esters, phenyl salicylates, crotonic acids, malonic esters, organoacrylates, hindered amines, hindered phenols, or triazines, and the ultraviolet ray absorbing group includes a residue of benzotriazoles, hydroxybenzophenones, esters of benzoic acid or salicylic acid, acrylates, alkoxycinnamates, oxamides, oxanilides, benzoxazinones, or benzoxazoles; α is an integer of 1-8; β is an integer of 1-8; and γ is an integer of 1-8. X is a 3-10 valent organic group; R a is Rf-PFPE-; Rf is C 1-16 -alkyl optionally substituted by one or more F atoms, and preferably is C 1-16 -perfluoroalkyl; PFPE is a group of the formula: -(OC 4 F 8) a -(OC 3 F 6) b -(OC 2 F 4) c -(OCF 2) d - wherein a, b, c and d are each independently an integer of 0-200, ( a + b + c + d) ≥ 1, and the occurrence order of the respective repeating units in parentheses with the subscript a, b, c or d is not limited in the formula; Rf is C 1-16 -alkyl optionally substituted by one or more F atoms, and preferably is C 1-16 -perfluoroalkyl; PFPE is a group of the formula: -(OC 4 F 8) a -(OC 3 F 6) b -(OC 2 F 4) c -(OCF 2) d - wherein a, b, c and d are each independently an integer of 0-200, ( a + b + c + d) ≥ 1, and the occurrence order of the respective repeating units in parentheses with the subscript a, b, c or d is not limited in the formula; R b is -Z-SiR 1 k R 2 l R 3 m; Z is O or a divalent organic group; R 1 is R b ' which is defined as R b; R 2 is OH or a hydrolyzable group; R 3 is H or lower alkyl; k is an integer of 0-3; l is an integer of 0-3; m is an integer of 0-3; in R b the number of Si atoms which are straightly linked via the Z group is ≤ 5, in one R b ( k+l+m) = 3, and in formula at least one l is ≥ 1; Z is O or a divalent organic group; R 1 is R b ' which is defined as R b; R 2 is OH or a hydrolyzable group; R 3 is H or lower alkyl; k is an integer of 0-3; l is an integer of 0-3; m is an integer of 0-3; in R b the number of Si atoms which are straightly linked via the Z group is ≤ 5, in one R b ( k+l+m) = 3, and in formula at least one l is ≥ 1; R c is a radical scavenger group or an ultraviolet ray absorbing group, wherein the radical scavenger group includes a residue of benzophenones, benzotriazoles, benzoic esters, phenyl salicylates, crotonic acids, malonic esters, organoacrylates, hindered amines, hindered phenols, or triazines, and the ultraviolet ray absorbing group includes a residue of benzotriazoles, hydroxybenzophenones, esters of benzoic acid or salicylic acid, acrylates, alkoxycinnamates, oxamides, oxanilides, benzoxazinones, or benzoxazoles; α is an integer of 1-8; β is an integer of 1-8; and γ is an integer of 1-8.