Here is a little help for the installation and removal, as well as for the correct measurement of profile locking cylinders..
Measure the locking cylinder correctly
Figure 1 u. 2: Measure from the middle of the forend screw or fastening screw to the outer edge of the fitting or rosette, on both sides.
Figure 3 u. 4: Measure from the middle of the forend screw or fastening screw to the outer edge of the locking cylinder, on both sides.
Lock cylinder removal
Lock cylinder installation