Selectively cold-water responsive compositions constructed of combinations of polymers including at least one hydrolytically degradable polymer and at least one cold-water soluble polymer are provided. The structure includes at least one side wall and an end wall attached thereto. And, a C-shaped stop ring, having a slit on its periphery and disposed within a tapered portion of a hole portion of the cap nut, is provided. The exchange coupling layer may be between the first and second pinned layers, and the second pinned layer may include a ferromagnetic layer and a non-magnetic layer. This light source may be used where light of adjustable color is needed, for example in a theatrical spotlight or a liquid crystal projection system. In particular, these unique and improved compositions can be produced using conventional, commercial-scale processes.