Linearführung, MGN9C-Lagerstahl, Leichte Miniatur-Lineargleitschienenführung, mit Schlittenblock, für Miniaturisierte Geräte (600mm)

This rail from Yunir came in the typical heat-sealed plastic pouch with a small plastic rail section for removing the block/carriage and three ball bearings floating around the bag. Which is more than a little concerning as there is no mention of spares included, so the block has managed to come far enough off the rail in shipping or storage to have a few bearings to jump loose from the retainers. When inspecting the carriage there are several gaps in the bearings on either side, a one ball gap is entirely normal but there are several. This happened for two reasons, the first is that the bag used for the rail is too long and leaves enough room for the block to almost entirely leave the rail and the rubber stoppers had worked loose in the packaging.So the first thing I had to do was partially remove the block and replace the bearings that had managed to jump loose in the packaging, which I'm fortunately experienced enough to do, but a customer really shouldn’t need to do this. Once I had the bearings back in place the overall quality is on par with any of the budget import rails these days which is getting surprisingly good, it feels a bit scratchy and rough right out of the packaging because it’s got no shipping oil or grease, but once you’ve cleaned it up and added some grease it slides without any noticeable slop, roughness or other issues.The seller has made no reference or mention of what clearance or tolerance class it is, which is something I'd prefer to see if possible but it’s not a huge issue for a lot of applications. It’s also not going to match the name-brand stuff like for like, but unless you’ve got an exacting project that demands or justifies the best this is more than good enough. Especially when you’re paying a fraction of the cost per rail and you might be using a half dozen of them on a given thing, like a 3D printer build etc.It’s a good thing they’ve included the plastic piece for sliding the block off the rail and as like any cheap rail it really benefits from a proper rinse and clean with some solvents to remove any leftover swarf and contaminates from the manufacturing. The bag the rail arrives in is actually a decent container for soaking the rail and block in IPA or something similar, just cut one end off the bag and fill it up and you’ve got the perfect container for cleaning the rail.Aside from the loose bearings on arrival my only other complaint is about the overall length being 2-3mm short of what’s advertised and that the cut end looks to be lazily done by hand as it’s badly angled and unevenly chamfered. Thankfully the burrs from the cutting have been removed and it doesn’t seem to be discoloured from overheating so it’s perfectly functional but if you need a rail that’s exactly 300mm or perfect aesthetically this is not the best option.The £17.35 pricing on the 300mm is marked up a little over what I’m used to paying for similar rails direct from China but if you need a MGN9C rail in 400, 500 or 600 millimetres sizes on short notice and you’re alright with potentially having to put some bearings back in place it’s alright.