This is an evolution of my project http://www.thingiverse.com/thing:793689. The new universal X plate carriage is screwed to the upgraded linear bearings SCS8LUU can fit 2 different mounts for single or double extruder. It is very simple to change the support for one or two estruder through the two M5x16 screws mounted on the back of the carriage between the bearings without dismantling the carriage from the bearings. Are also included two types of mount for the cooling fan of extruder that you can download together with the other parts required at the links listed below: Single extruder fan from: http://www.thingiverse.com/thing:354723 Dual extruder cooling fan, nozzle cooling fan mount (single or double), dual extruder clamp and servo and arm for auto bed leveling from: http://www.thingiverse.com/thing:793689