I suggest take your time to align correctly if you elect to stack. I watched their installation video on youtube and was surprised at how easy it was to take off my old ear pads and install the new ones! Noise cancellation is not the best but definitely above average. My daughter isn?t hard on shoes, and rarely wears them even though she likes them. The rubber is also crumbling. But it seems to work great when on my bike. Holds 10 pairs of flats and sandals easily and takes up no space in my closet! I use them when working out and they?re comfortable. Then, finally, one of the wires for the left side severed. Its also great for films and gaming due its large soundstage and dialogs will sound absolutely delightful on these.