It is an object of the present invention to provide a curable which has good storage stability and can give cured products retaining the high elongation characteristic originating from the polyether polymer and showing a high gel fraction and good weatherability.Thus, the present invention provides a durable compositionwhich comprises the following two components:a polyether polymer having at least one crosslinkable functional group anda vinyl polymerwhich is compatible with said polyether polymer having at least one crosslinkable functional group at a polymer terminus.Further, the present invention provides a curable compositionwhich comprises the following three components:a polyether polymer having at least one crosslinkable functional group,a vinyl polymer incompatible with said polyether polymer and having at least one crosslinkable function group, anda compatibilizing agent capable of compatibilizing said polyether polymer and said vinyl polymer with each other when added to a mixture thereof.