Abstract: A cap assembly for use with multiple bottles having different size necks is provided. The assembly includes a base, at least one adapter and a lid. The base includes a compartment for storing the adapter and an opening having at least two internally threaded sections of different size and a port. The adapter includes an internally threaded opening having at least two sections of different size and an externally threaded surface having at least two sections of different size. The lid is mounted on the base for movement between a position wherein the base opening port is closed and a position wherein the base opening port is open. Additional adapters may be included. The additional adapters are configured to accept bottle necks of different sizes than the base opening and first adapter such that at least six bottles with different size necks can be used with the assembly.