I Had a problem when using a PLA bushing for my new prusa x-carriage, i found that a PLA bushing seem no good to holding on a X Axis Rod and make it less gap btw them. So, i redegin a whole x-carriage by using a PTFE as a bearing and I also using a two side screw tensioner fit onto x-carriage, it works very fine for me to tightened X axis belt just by (un-tightened 2nos M3 belt clamps screw + turning screw tensioner as you want how x belt to be tighten).However, I notice that this design may be no suitable for whom who is using a two supporting screw to holding a hot-end nozzle, due to the opening of this carriage is not to big. (What i'm using is PEEK sleeve inside with PEEK thermal barrier, So, i dont need that supporting screw.)BOM List.