A one-part room temperature vulcanisable (RTV) silicone composition which comprises (a) an organopolysiloxane polymer having at least two hydroxyl or hydrolysable groups per molecule of the formula X 3-n R n Si-(Z) d -(O) q -(R 1 y SiO (4-y)/2 ) z -(SiR 1 2- Z) d -Si--R n X 3-n in which each X is independently a hydroxyl group or a hydrolysable group, each R is an alkyl, alkenyl or aryl group, each R 1 is X group, alkyl group, alkenyl group or aryl group and Z is a divalent organic group; d is 0 or 1, q is 0 or 1 and d+ q = 1; n is 0, 1, 2 or 3, y is 0, 1 or 2, and preferentially 2 and z is an integer such that said organopolysiloxane polymer has a viscosity determined in accordance with the method outlined in the description of from 10,000 to 75,000 mPa.s at 25°C, alternatively from 10,000 to 60,000mPa.s at 25°C; (b) a reinforcing filler comprising or consisting of fumed or pyrogenic silica filler which may optionally be hydrophobically treated, in an amount of from about 5 to about 25 parts by weight per 100 parts by weight of organopolysiloxane polymer (a) (c) a silane adhesion promoter in an amount of from 0.10 to about 2.0 parts by weight per 100 parts by weight of organopolysiloxane polymer (a) (d) a catalyst comprising (i) a titanate and/or zirconate and (ii) a metal carboxylate salt; and optionally (e) and/or (f) wherein (e) is a cross-linker (f) is a hydroxy scavenging agent selected from a disilazane or polysilazane. (a) an organopolysiloxane polymer having at least two hydroxyl or hydrolysable groups per molecule of the formula X 3-n R n Si-(Z) d -(O) q -(R 1 y SiO (4-y)/2 ) z -(SiR 1 2- Z) d -Si--R n X 3-n in which each X is independently a hydroxyl group or a hydrolysable group, each R is an alkyl, alkenyl or aryl group, each R 1 is X group, alkyl group, alkenyl group or aryl group and Z is a divalent organic group; d is 0 or 1, q is 0 or 1 and d+ q = 1; n is 0, 1, 2 or 3, y is 0, 1 or 2, and preferentially 2 and z is an integer such that said organopolysiloxane polymer has a viscosity determined in accordance with the method outlined in the description of from 10,000 to 75,000 mPa.s at 25°C, alternatively from 10,000 to 60,000mPa.s at 25°C; in which each X is independently a hydroxyl group or a hydrolysable group, each R is an alkyl, alkenyl or aryl group, each R 1 is X group, alkyl group, alkenyl group or aryl group and Z is a divalent organic group; d is 0 or 1, q is 0 or 1 and d+ q = 1; n is 0, 1, 2 or 3, y is 0, 1 or 2, and preferentially 2 and z is an integer such that said organopolysiloxane polymer has a viscosity determined in accordance with the method outlined in the description of from 10,000 to 75,000 mPa.s at 25°C, alternatively from 10,000 to 60,000mPa.s at 25°C; (b) a reinforcing filler comprising or consisting of fumed or pyrogenic silica filler which may optionally be hydrophobically treated, in an amount of from about 5 to about 25 parts by weight per 100 parts by weight of organopolysiloxane polymer (a) (c) a silane adhesion promoter in an amount of from 0.10 to about 2.0 parts by weight per 100 parts by weight of organopolysiloxane polymer (a) (d) a catalyst comprising (i) a titanate and/or zirconate and (ii) a metal carboxylate salt; and optionally (e) and/or (f) wherein (e) is a cross-linker (f) is a hydroxy scavenging agent selected from a disilazane or polysilazane. <EOS>