Based on my experience with the entire Double Blade series, I feel the posted measurements online doesn't necessarily equal how tight each tip will feel on a particular IEM nozzle, especially since I know that based on application, the Cp240 does not have the narrowest fit of the series. There are some IEM nozzles that are really wide (for example the 1MORE Quad Driver), and even though the CP240 is a small diameter for the Quad's nozzle, it will still fit if you take a few extra seconds and muscle to fit the CP240 on the nozzle. If you need a smaller diameter tip (as narrow as a Shure or Westone nozzle), then the single flange CP800 is the best fit.