I find that the regular Creality Splice Kit for the CR-30 3DPrintMill a bit long for everyday use in my space limited apartment. This 3D printed version gives you an extra 180 mm for parts to roll out. The vertical height of the roller are adjustable via 6 M5 bolts with M5 hex nuts inserted into the rails.
Rollers should be printed with the asterisk facing up at 0.3mm layer height. You can find more details on my site.
Hardware:
4x - M5 x 20mm
6x - M5 x 40mm
6x - M5 Washer
6x - M5 Hex Nut
6x - 605ZZ Bearing (Inner Dia.=5mm, Outer Dia.=14mm, Thickness=5mm)
The author hasn't provided the model origin yet.