Linear Guide Rail Mini High Accurate Linear Rail Guide with Professional and Technical Rail and Sliding Block for CNC Machine (400mm)

Very happy with this item got to upgrade a 3d printer / and has involved quality.

aliexpress price with next day prime delivery. very nice quality considering cost

I bought 4 of these rails for a project. I knew there would be issues but had hoped with some effort could resolve them and get them working "well enough".On the positive side: the individual rails were safely packed, I didn't open the packaging to a cascade of ball bearings. The ball bearings themselves are the correct 3/32" in size (2.381mm) and they appear to have the correct number. When I stripped the carriages down I did not find metal swarf that you often find in cheap carriages like these so I take that as a positive (they were still absolutely covered in gunk/storage-oil for shipping)On the not so positive which I found when stripping and cleaning the carriages: the guide wires (for holding in the ball bearings) are very (very) slack. They appear straight and there's no obvious cause that i can see but they're very slack and don't really secure the ball bearings in the races. The bearings fall out *incredibly* easily. The balls do not circulate in two of the carriages smoothly (which coupled with the loose guide wire is a recipe for disaster).Basically after careful cleaning , striping and rebuilding I have two "working" carriages. I say "working" as they're not exactly smooth (you can feel them bind on the rail at a couple of points) but there appears to be no detectible play in them. I put the lack of smoothness down to the rails being less than perfect (and for the money is to be expected). The other two carriages bind, grind and require excessive force to move along the rail.So basically a 50% success rate.It's a bit of a cost-balancing act, with cheaper rails you have to expect a less than 100% success rate. However, my impression was that I was "lucky" and I suspect if I bought more rails or carriages than that success rate would drop. If, for example, I'd only got one rail/carriage working out of the 4 then I would've been better simply paying more and buying on-brand.The old adage applies - "buy cheap, pay twice" As I said in the subject: YMMV

I recommend