I bought this to replace my old Makita DTM50Z Multi-tool, which finally stopped working after years of heavy use. The 51Z has a major improvement over the 50Z, which is the tool-less accessory clamp that secures any attachment you put on the machine. With the 50Z, if you put a saw blade on the machine you had to use a hex wrench to secure the blade. Unfortunately, when using the 50Z the vibration would make the saw blade work loose quite quickly, which was extremely annoying. The tool-less accessory clamp on the 51Z is a massive improvement. The only downside with the 51Z over the old 50Z is that the latter had a light that came on in use, whereas the 51Z no longer has a light, doubtless due to the new accessory clamp being in the way. In conclusion, I would definitely recommend the 51Z over the old 50Z - it’s a much better machine.