Recessed sockets(2-pin legacy products) – These move the cable end further into the shell and provide a more sturdy mounting point for the cable and the pins of the cable thus protecting it more. Recessed sockets can trap moisture and dirt in some casesAmbient ports – This allows a customer to not feel so isolated by allowing ambient/outside noise in with the in-ear monitors inserted. A ambient plug tree with different size plugs is included with this option. Note that if any plug other than the solid one is used bass response is greatly reduced. **May not be compatible with all models/customer ear shapes.Soft canals(discontinued) – This material is used on just the canal portion of the in-ear monitors, it softens with body heat. Used mostly by customers with sensitive canals, singers, and people that move there jaw a lot during activities. More maintenance is required with the soft canal option as the material is not as durable as hard acrylic. **May not be compatible with all models/customer ear shapes