Wide bore is<<< Stem inner diameter. Excuse the copy and paste below (not an advert) - just easier to explain. > Symbio W eartips – bore diameter 4.5mm. > Symbio Wa eartips The Symbio Wa has bore diameter cca. 2-2.5mm, neutral influence to the IEMs sound signature. Allows high frequency details and energy. Perfect seal for best bass. These eartips comes with adapters for IEMs like Shure SE846 (…) Westone UM Pro 50 (…) and all In Ear Monitors with 2-2.5mm stem diameter. > Symbio Wn eartips Silicone+Memory Foam Special Hybrid Universal Ear Tip. For In Ear Monitors with stem diameter of 3-4mm. > Symbio W Peel eartips Simple Single Flange Silicone EartipsBore diameter 4.5mm.