My first shield cracked within the first week. My phone charges quickly and I am amazed how quickly I am back in business. I actually have two pairs of cans and yes, the amp drives them both at insanely high levels at the same time with a cable splitter ! If they hold up for a year or two they are definitely a bargain. I bought these as a replacement for my Bose ae2i Bluetooth headphones after the Bluetooth adapter went bad. My order didnt come with all of the tools and items shown in the photo, which was the whole reason I wanted it. Bottom line - they just work. Thats great but after 15 minutes, who can remember?All in all, Im only partially happy with this device and will continue my quest for the perfect Skype / remote support headset that can also play stereo music. One rail has four allen screws, two on each side. Really thick, & fits the bar well without even using the straps to secure it.