Ortlieb says about the 2 QL2.1 Hooks With Adjustable Strap 18 Mm
For all models with the QL2 or QL2.1 system />If the standard mounting hooks are too small to fit on the tubes of your bike rack, simply replace the standard hooks with a set of 18-mm ORTLIEB hooks (cannot be used with inserts).
+ 2 QL2.1 mounting hooks (18 mm) and adjustable handle