8x19x6 Metal Halo bearing by Avid Racing Concepts is a new bearing used in the Serpent 811-Be for the diff pinions replacing one of the 13x19's in the front and rear diff. So instead of running (3) 13x19's per diff for the V2 Coupler or (2) 13x19's for the V1 Coupler, the new V3 Coupler uses (1) 13x19 and (1) 8x19. The Serpent 811-Be uses 2 of these and they never come in contact with the outside world (dirt) which is why they are metal shielded. Check your manual for the correct size for your vehicle if you are not certain.