Messenger bag

Left shoulder bag
1000d military green Cordura
lightweight vinyl waterproof layer 
red 200d nylon liner with 3 internal pockets
Nylon buckles
27 liters 
15”(38cm) x 13” (33cm) x 8.5” (21cm)
What we now think of as the modern bike messenger (courier) sling bag started life back in the ‘50s when the De Martini Globe Canvas Company designed a bag to be used by phone company workers. The bags were made to accommodate all the tools they needed to work with, so the bags were very spacious and functional, with a large flap closure and a thick strap to be carried over one shoulder and across the body. In 1965 NYC bike messengers started to use these bags to deliver packages. By the late ‘70s the big NYC courier companies would order custom De Martini bags for all of their riders. In these pre-internet (and pre ECMC/CMWC/NACC) years it took a while for the De Martini bags to start showing up in other US cities, mainly brought by traveling bike couriers. One of these bags happened to fall into the hands of San Francisco courier Erik Zo. Most SF couriers would ride cruiser style bikes with baskets to carry their packages. The De Martini bag would allow couriers to ride lighter road (and later track) bikes, and carry the packages on their backs. These bags shared a similar pattern to the modern messenger bag, but they were made from heavy sail cloth canvas, and were not waterproof. They would also wear out quickly with year ‘round daily use of courier work. Erik knew he could do better, and in 1983 the Zo bag was born, made from quality Cordura fabric and lined with (waterproof) PVC truck tarp. Erik is still making bags in small numbers to this day, but getting your hands on one is difficult, and (rightly) expensive. 
Many companies have made their version of a messenger sling bag since Eric made the first Zo bag, this is my love letter to a timeless classic. Really, you should buy a @zo.bags bag, but if you can't, you should buy one of these.