2011 Outlaw 50 rear brake seal?

New to the forum, but not Polaris. Replacing rear axle bearings and seals in my kids 2011 Outlaw 50, and came across something in the parts diagram when getting a parts list together. What seal is item 21 (p/n 0451781) in the attached parts diagram? Item 14 (p/n 0450430) are the seals that go on both sides of the axle housing to seal the axle bearings. Have no clue what item 21 is and according to the parts diagram, only 1 is required. I have my kids Outlaw apart and only had 2 identical seals pressed into each side of axle housing. Not sure if I’m missing item 21 (p/n 0451781), or not? TIA.