Controlled Substances
 

C-I
The controlled substances in this schedule are those that have no accepted medical use in the United States and have a high abuse potential. Some examples are heroin, marijuana, LSD, peyote, mescaline, psilocybin, THC, MDA, ketobemidone, acetylmethadol, fenethylline, tilidine, methaqualone, dihydromorphine, and others. 

C-II
The controlled substances in this schedule have a high abuse potential with severe psychic or physical dependence liability. Schedule II controlled substances consist of certain narcotic, stimulant, and depressant drugs. Some examples of Schedule II controlled narcotic substances are: opium, morphine, codeine, hydromorphone, methadone, meperidine, cocaine, oxycodone, anileridine, and oxymorphone. Also in Schedule II are amphetamine and methamphetamine, phenmetrazine, methylphenidate, amobarbital, pentobarbital, secobarbital, fentanyl, etorphine hydrochloride, and phencyclidine. 

C-III
The controlled substances in this schedule have an abuse potential less than those in Schedules I and II and include compounds containing limited quantities of certain narcotic drugs and nonnarcotic drugs such as: derivatives of barbituric acid except those that are listed in another schedule, glutethimide, methyprylon, nalorphine, benzphetamine, chlorphentermine, clortermine, phendimetrazine, and paregoric. Any suppository dosage form containing amobarbital, secobarbital, or pentobarbital is in this schedule. 

C-IV
The controlled substances in this schedule have an abuse potential less than those listed in Schedule III and include such drugs as: barbital, phenobarbital, mephobarbital, chloral hydrate, ethchlorvynol, ethinamate, meprobamate, paraldehyde, methohexital, fenfluramine, diethylpropion, phentermine, chlordiazepoxide, diazepam, oxazepam, clorazepate, flurazepam, clonazepam, prazepam, lorazepam, alprazolam, halazepam, triazolam, mebutamate, dextropropoxyphene, and pentazocine. 

C-V
The controlled substances in this schedule have an abuse potential less than those listed in Schedule IV and consist of preparations containing limited quantities of certain narcotic drugs generally for antitussive and antidiarrheal purposes.

Controlled Substances in More Detail

It is clear that you do not want to be buying, or importing, any of those unless you are sure of what you are doing. The fact that some online sites are advertising almost every item listed does not mean they will deliver it or that it is legal for you to buy.