The present invention concerns a sizing composition for glass fibres comprising: (a) A silane based coupling agent mixture, (b) A film former, (c) Additives, Characterized in that, the silane based coupling agent mixture comprises (d) At least 15 wt.% of at least one dialkoxysilane, and (e) At least 20 wt.% of at least one (meth)acryloxysilane, wherein the wt.% are measured with respect to the total active solid weight of silane based coupling agent. The present invention also concerns a polymeric composite reinforced with such glass fibres.