Onoto washer 7.78mm (5x)

Suitable for 'O' and 'N' type pens, models 1000, 2000, 3000, 3500, 4000 and ringtop models this washer is 7.78mm diameter and normally does not require a 0.5mm backing washer in the installation due to the plunger having a recess for the top flange.
However, some plungers for this type of pen are of a flat design and need the backing washer. These are included free in the price.

Price is for 5 washers and 5 backing washers.