Abstract: A mask that protects the edges of the gear teeth of a gear during a particle impacting process, such as a shot peen or other similar process, without preventing the particle impacting process from effectuating advantageous hardening and other results for areas that are not protected by the mask. The cover may be removable and reusable. The mask may include a closed end and an open end, with a plurality of protective vanes extending between the two ends. The gear may be received within the mask and aligned and secured such that the vanes cover the gear teeth edges, thereby protecting the edges from the particle impact process, without preventing the particle impacting process with regard to other portions of the gear teeth.