2PCS Linear Rail SBR16 500mm + Ballscrew SFU1605 500mm Set Includes 4pcs SBR16UU Bearing Block, Coupler, BK/BF 12 and Screw&Ball Nut Housing, for CNC Machine

I've seen a few reviews that were negative mentioning poor fit. Perhaps, but you know all of this, including the ball size for the lead screw are adjustable. For the price paid and the materials offered, I don't think you can go wrong. Especially if this is your first build. Realize going into this project that you need a DIY mentality. If things don't fit initially the way you thought, you might have to adjust your thinking! Yes, this is raw material you're working with not a pre-built 3D whatever your building. You may need to shim it, adjust it, repack with larger bearings but the thing is these are easily accomplished and this is essentially a kit that takes the guess work out of a large part of your build. I'm pleased, it's not perfect but it's really, really close for the price. I'll buy it again - in fact I DID!UPDATE: I would agree with dcoombs on one thing. Don't bother trying to use the mounting holes drilled on the rails or the dimensions for the hole spacing that is provided in the specs. In rare circumstances they might actually match. Instead wait until you get the rails in hand and make your own mounting holes. This way you'll have complete control over the end result. I built a highly accurate cross-slide vice to use on my drill press as an intermediate step to building a CNC. For my purpose I'm satisfied with the product and the end results. If I had one recommendation for the supplier it would be to provide the rails without mounting holes, at least as an option.

This isn't the most precise system you'll find, but it's quite good for the price. It comes with everything you need except for M5 screws to hold things together. There are no directions, but most things fit together intuitively. If you want something with documentation and warranty support, McMaster probably has something 10% better for 10 times the cost.

Better quality than the kit I ordered before. And everything I needed came with. Didn’t have to order anything separate.

The mounting holes are too large on the SBR rails at 6.25mm on a 10mm flange. Do not drill/tap mounting hole locations until you receive the physical parts. You will have to mark by hand each inaccurate hole center based on the actual hole locations. Do not rely on documentation in this regard.

full kit of ball screw, bearings and linear shaft, Arrived before committed date.

this is exactly what it says, good quality too

Quality is good, works great