The pulley it's replacing was plastic, so nice upgrade. Also allowed for a more "round" number for my steps/mm on the X. Good quality machining and finishing.

The pulleys themselves work great, but here's a little advice for anyone building their own RepRap: stick with 16, 20 or 25 tooth pulleys if you're using (ungeared) 1.8 or 0.9 degree stepper motors. Using 16, 20 or 25 teeth create steps/mm values in the firmware that are round numbers, meaning less positioning error by your printer. Given, this error is tiny enough that you probably won't ever see it (I've used a 15-tooth pulley on my Prusa i3 for ages and it makes beautiful prints), but it might add up when dealing with Delta or CoreXY kinematic systems. The bigger factor to keep in mind is that more teeth on a pulley result in more speed but less torque. (More teeth also theoretically decreases the XY resolution, but this drop is so tiny that it really isn't a problem.) So if you're building a machine with a lightweight print head and want lots of speed, opt for a higher tooth count. Otherwise, this 16-tooth pulley should fit the bill for most typical Cartesian designs!

Just what I needed to complete my Delta build, fast delivery great service.