2 PCS HGR15 Linear Rail+4 PCS HGH15CA Slide Block Smoothly: Very high load carrying capacity,Smooth running, low noise and non-pollution Convenient: Easy to assemble and interchangeable, you can replace the slider or the guide rail or even the linear guide group respectively Low Consumption: No stick-slip effect, heats up less, reduced drive power required Wide Application: The linear guide rail can be applied to DIY CNC routers lathes and mills.etc