A moisture curable composition comprising (A) a polymer containing reactive hydroxyl or hydrolysable groups bonded to silicon which groups are reactive in the presence of moisture; (B) a crosslinking agent comprising at least two and preferably at least three groups reactive with the silicon-bonded hydroxyl or hydrolysable groups of polymer (A); (C) one or more reinforcing and/or non-reinforcing fillers and (D) 15 to 30% by weight of the composition of a silane having the structure: (R1)m (Y1)3-m Si - Z1 - G1 - Z2 - Si ( R2)q (Y2)3-q in which R1 and R2 are alkoxy groups containing from 1 to 6 carbons, Y1 and Y2 are alkyl groups containing from 1 to 8 carbons, Z1 and Z2 are alkylene groups having from 1 to 12 carbons, G1 is a chemical group containing a heteroatom with a lone pair of electron; and m and q are independently 1, 2 or 3. Silane (D) is provided to function as the cure catalyst.