The VERT X1 is a smart phone bag - a convenient and accessible way carry your phone when you ride. A quick release clip means you can easily take your phone or mp3 player with you when you leave your bike. It has a bracket that mounts to the top cap of most bikes that have clamp-on stems (see 3rd photo). This is for small devices with max size of about 2.25"x4.5". The pouch is about 3"x5" outside when measured pressed flat. This doesn't work with most newer smart phones.
