The component with the lowest price in the E-11 schematic is the Circlip,in,24.
In this schematic the "Spring,clutch" is used most often.
Parts such as the E-11: Circlip,in,24, Circlip In 25mm, Clip,ex,30x2.0, Brg,needle 17x25x are included in the Nps50 Zoomer 2008 (8) Japan Af58-170 E-11 parts fiche.