R4A 2RS 1/4" X 3/4" X 9/32"
E-bay 10@$13.75 shipped, not bad.
http://www.ebay.com/itm/160757033936?ss ... 1439.l2649
I have them installed on my X and Y axis, I found that I need 10x32 (I think that's the size) washers on the outside so that I give the center race some thickness so that it doesn't bind or rub against the plastic washers.
I will post pics later tonight for assembly and installed.
I definitely notice a substantial difference in print quality between the plastic idlers and these bearings.