Locate the euro cylinder fixing screw on side of the door locking strip, It is the one that lines up with the bottom of the barrel cylinder. see photo.

Once the euro cylinder screw is fully removed, turn the key to face approximately “10 past” on the clock (see picture) then pull the cylinder out slightly jiggling the key.

This will allow the euro cylinder to be removed. In some cases some slight turning of the key will help the barrel come out easier, also loosening the bolts on the handles can help the euro cylinder to be removed if it is tight.

Pull out the cylinder fully and place on suitable surface to measure

To measure a cylinder you have to measure the distance from the centre screw hole to the outside of the cylinder on one side and then do the same on the other.

So the barrel in the picture would measure as a 40/60. On the order screen you would order size = 40 , size B = 60.