Plastic Nylon Hex Standoff Male FemaleThreaded Spacer Pillar M3 Thread 6+6mm 100Pcs

Won't hold thinner PCBs reliably, as the inner threads are a bit shorter than other standoffs

These standoffs are a reasonable offering for the price. Thread quality is not of the highest quality, but with some tweaks (removing extra plastic molding bits, etc.) work for small volume projects. If you need tight tolerances, I would recommend looking into brass standoffs as they tend to be of higher quality. (But at a higher price as well.)