The 3/8 x 5/8 x 5/32 R1038-RSZC Ceramic Revolution Series bearings are a low friction high quality steel/chrome bearing with metal shields and ceramic Si3N4 balls. What makes this bearing unique is that it has a rubber seal on one side while having a metal shield on the other. Rubber seals are great protectors against dirt but the price is that they offer a little more friction due to the tighter seal.
3/8 x 5/8 x 5/32 R1038-RSZC Ceramic Revolution bearing by Avid Racing Concepts is the standard bearing for Associated diff outdrives. Check your manual for the correct size for your vehicle if you are not certain.