Made from from PLA, a 100% biodegradable, plant-based plastic substitute! Each disc is imprinted in both US and mm needle sizes from US 0-15 / 2-10 mm. We have long wanted a tiny needle gauge tool for travel-knitting. The big squares or rectangles are okay for at-home knitting, but clumsy for travel - so we fashioned one based on those a jeweler would use to size diamonds.