Simple to use and comfortable to wear on a bike, courier and office bags are a great way of carrying bulky, awkward loads whilst on your daily commute. Most have a large main compartment and a variety of smaller pockets for keys, phone or even your laptop. The fold over top on the courier/messenger style bags means access to items is quick and easy. A chest strap will help stop the bag swinging around off your back when riding and will improve comfort.