The Makeblock Rectilinear Motion Robot Pack contains four kinds of Makeblock components, mainly used to build linear motion mechanisms. For example, attach a nylon pulley to Makeblock beams to give your robot a smooth linear motion.
Parts List:
 
No.
Part Name
QTY
1
Threaded Shaft 4x39mm
4
2
Shaft Collar 4mm
4
3
Nylon Pulley with bearing
4
4
4X8X3MM BEARING
8
5
Headless Set Screw M3x5 
4
6
Nut M4
4