Genetics: Runtz x Wedding Crasher x SB x KC 36. RSO is a decarboxylated full spectrum extract. RSO is short for Rick Simpson Oil, and is also commonly referred to as ‘FSO’ for ‘Full Spectrum Extract.’ Full spectrum means it contains all the cannabinoids, terpenes, and many other valuable compounds found in the cannabis plant. We hope that the interaction of all the compounds of the plant, all concentrated together in this powerful oil, provides you with the same relief it has for many others.