2PCs 8mm x 300mm (.315 x 11.81 inches) Case Hardened Chrome Plated Linear Motion Rod Shaft Guide - Metric h8 Tolerance

I have tested several rods using a dial indicator to check for straightness. I use the HF digital dial indicator on a magnetic stand. The key to getting consistent results is to have a follower that rides on top of the rod so that minor xy position error does not affect the dial indicator reading. I use a piece of glass as it provides a perfectly flat surface to the rod. Good stock rods are typically <0.05mm out of round. Unfortunately one of my boxes was damaged in shipping, but one of the rods was undamaged. It measured better than 0.01mm!. The second set of rods arrived in perfect condition with high denisty foam separating the rods and protecting them from the box at 5 different points. Customer service was excellent for the damaged box. I will update when I get a chance to test the second set of rods

These were perfect for my project, which is a custom start gate for a Pinewood Derby track. Both rods were perfectly straight. They cut easily with my chop saw and a 7" diamond metal cutting blade. Dimensions were as advertised. Shipped promptly and arrived on time.

Rods were of consistent size and straight, time will tell how they will wear but I'm optimistic.

Looks great, used these for an art piece. Perfect description!

Precise size for my project. Used it as clamping surface of a mini mill table so I could square up the ends with a larger mill

They were about 5mm too short for the bed of my Robo R1+ but I was able to make some spacers to deal with the problem. Nice quality other than that small problem.

Precision machined and looks great!

I didn't use these for robotics, CNC, or 3D printing, but they were absolutely perfect for the project they were purchased for. I didn't spend much time on any measurements, but they were consistent enough for what I was doing. I wouldn't hesitate to buy them again.