X-Mini II XAM4-S Portable Capsule Speaker, Mono, Silver 40mm Driversgives you that extra edge over 36mm drivers when it comes down to sound quality. it is not that 36mm are bad, it is just that we have made 40mm better! Bass Xpansion System(BXS)- supports the 40mm drivers in delivering that much needed bass on mini portable speakers. Connect several different X-miniCapsule Speakersto 1 X-miniHAPPY Capsule Speakerand you are all set. 3.5mm audio cable- is easily kept away beneath the base of the Capsule Speaker. Stow-away takes away the hassle of wires especially when you are on the go. Playbacktime tripled to 12 hours for longer, superior on-the-go audio