These are another z-rod stabilizer for Printrbot+. I made this data before mikemwa upload his one so I did not compare this with his stabilizer. The holes for z-rod of my PB+ are loose. So z-rod are not perpendicular and always wobbling. These help to stabilize z-rod and reduce wobbling.
Print L & R. 12mm hole will be too tight. File the hole. Do not file too much.
If your z-rod is inclined like mine, printing longer sleeve may be difficult. Print temporary version with low infill and install it. Then, print actual stabilizer.