The Furutech FI-15 Plus IEC connectors actually have a very tight fit when inserted into equipment. This is both with the plug casing itself (which the fit into the IEC socket is very tight and snug) as well as the strength of the internal contact clamp mechanism. The more expensive Furutech connectors are still pretty okay, but not quite as tight fitting.
The Neotech IEC connectors are tight fitting as well.
The Neotech IEC connectors are tight fitting as well.