The topeak rx trunk bag ex is small and compact but with enough room to store 28 litres making it great for commuting the ex trunk bag does not have panniers on the side like the topeak rx exp so is ideal if you do not need too much space and want to easily carry the rack bag with you when you are off your bike it is supplied with a carry handle and shoulder bag and easily clips on and off your topeak rear rack using topeak39s patented quicktrack system elastic bungees on the top of the