A Runtime Callable Wrapper (RCW) is a proxy object generated by the .NET Common Language Runtime (CLR) in order to allow a Component Object Model (COM) object to be accessed from managed code. Although the RCW appears to be an ordinary object to .NET clients, its primary function is to marshal calls and data between a .NET client and a COM object. A Runtime Callable Wrapper (RCW) is a proxy object generated by the .NET Common Language Runtime (CLR) in order to allow a Component Object Model (COM) object to be accessed from managed code. Although the RCW appears to be an ordinary object to .NET clients, its primary function is to marshal calls and data between a .NET client and a COM object.