This Parts breakdown is for the following machines:
$13.10
Item # NPM458
Overall length 7-9/16 (shorter than NPM438)
$20.74
Item # NPM138
$15.28
Item # NPM402
Item # NPM418
$91.72
Item # NPM437
$21.84
Item # NPM441
$24.02
Item # NPM445
$10.92
Item # NPM405
$8.74
Item # NPM401
Item # NPM417
Includes: NPM401 Spring clip NPM418 Feeder Spring NPM138 Drive Blade NPM445 Plunger Spring NPM458 Blade Retainer
$52.40
Item # NPM172
Here are a few tips on using them.