Konjac prebiotics are high-purity glucomannan oligosaccharides (MOS) with a purity of 99.5%.
The following are government-tested COA.

Which is tested by : High Performance Liquid Chromatography, HPLC Coupled with Detector for Sugar.
And the calculated purity is based on the percentage: From Mannobiose to Mannodecaose.

Some people think that only Mannotriose to Mannodecaose  is oligosaccharides.
Actually Mannobiose is also oligosaccharides because it can not be absorbed by the body directly.

So if you are looking for glucomannan oligosaccharides, find Konjac prebiotics with a purity of 99.5%.