this is a derevitive of http://www.thingiverse.com/thing:10637 its a single print lm8uu holders for y axis. this helps with drilling the holder right in place, hence the extension along the y axis - these help to align ti perfectly. i did have to move the belt holders off center for the motor to fit, but it has no prformance effect, and has been tested on several prusa's by me.print, drill easly, enjoy.