A plug (10) is provided with a cavity (34) containing pieces of glass (35). When the plug (10) is drilled out the cavity (34) is ruptured and the disturbed glass (35) facilitates drilling of the plug (10). The plug (10) is made of a plurality of separate and distinct wiper elements (13) and spacer elements (14) which can be assembled to the required configuration before use. The plug (10) may be adapted to sit on a float collar having a hollow tubular body (102) and a seal plate (110) which is disposed across the hollow tubular body (102) and fixed thereto. The seal plate (110) has an outwardly extending plate (113) which sealingly contacts the inner surface of the hollow tubular body (102) and a bore for allowing fluid to pass.
