Ortlieb makes one of the best bike panniers in the world. All Ortlieb panniers sell in pairs. In their product listings there are many models but most cycle tourists would recommend the Classic series. The reason is because the Classic is made of PVC coated Polyester fabric and there are no external opening except the main compartment. This design will keep the whole bag waterproof and washing it off after a muddy ride is easy. Dirt will not get trapped in the fabric. You can literally throw the whole bag into the river and wash it with all the items in it and it will stay dry.
In the Roller Classic, there are many colors to choose and comes in two sizes, the Front-Roller Classic which is smaller and the Back-Roller Classic both with identical design. The capacity for both sizes are 25lts per pair and 30lts per pair. The Front-Roller Classic weights 1590g per pair and the Back-Roller Classic weighs 1900g.
In the Roller Classic there is only one main storage compartment. Inside the there are 2 storage pockets, one is open and the other zipper. Ideal for storing smaller items or flip-flop. Inside there is a plastic board the keeps the bag in shape.
To water tight the bag, roll the bag backwards and buckle the central clip. There are 2 options to buckle the side clip. One way as you can see here is to buckle them together and it becomes a carrying handle.
The back part of the bag is reinforce at the lower section where it comes in contact with bike rack.
The lower attachment can be removed for adjustment to secure to the bike rack
The Ortlieb QL-system is unique, to hook the pannier to the bike rack, you will need to pull the handle strap and this will open up both side of the clip. The QL system also provide 2 sizes of clips to fit your bike rack tubing. However I realised that there is a flaw because anyone can just pull the strap and take the panniers away. To prevent this from happening, tuck the strap away or keep it under the central buckle.
All the Ortlieb Roller Classic comes with a shoulder strap
This is another method of securing the pannier with the strap on
There is no left or right panniers, it can be mounted on either side. All panniers come with front and back 3M reflector.
On my bike I am using the large Back-Roller Classic and other the other is a Front-Roller Classic.
Ortlieb sells a Carry System that you can attached you pannier and it becomes a waterproof back back