For 1 bag: 2x8mm and 2x11mm; for all models with QL2 and QL1 from 2005
Inserts for QL2 hooks E166 for Ortlieb pannier bags.
Ortlieb pannier bags that use the QL2 system come with inserts to go inside the hooks, to allow the pannier bag to fit securely to a range of pannier racks of differing widths.
If you have lost yours, these are replacements that you can purchase. It's best to do this as soon as possible. Riding without any inserts means a loose-fitting hook on your pannier. This risks the pannier falling off when hitting big bumps and also will start to mis-shape the pannier hooks themselves. If they become too loose as a result, you will need to order the Ortlieb pannier rack hooks themselves, which is more expensive and takes longer to install.