It comes down to size and money -- especially money.

According to "Mark'', heroin costs $6,000 to $7,000 an ounce in Bermuda, compared to $2,000 for the same amount of cocaine and between $500 and $700 for an ounce of a cannabis.

But one ounce of heroin (28 grams) will yield between $800 and $1,000 per gram, meaning Mark can make a $20,000 profit from the single ounce that cost him $6,000 initially.

Each ounce is "cut'' (mixed) with four ounces of milk sugar which Mark then sells to other dealers for between $400 and $500 per half gram. These dealers divide it into as many as 40 hits, each of which will cost $20 -- double the wholesale price. By comparison, a hit of cocaine can cost between $100 and $125.

Top grade heroin smuggled out of Mexico or Amsterdam will go for $7,000 for an ounce, he says. While one half gram costs about $100 in the United States, in Bermuda it costs $500.

As a user's addiction grows, the drug will be cut more heavily, raising the dealer's profit -- although care is taken not to cut it so heavily that the buyer moves to another seller.

Aside from profits, heroin is also easier to smuggle than other illegal drugs.

An ounce of heroin can be smuggled into the island in pens, in the cover of a record album or in the lining of a belt.

HEROIN FACTS DGS Heroin facts Heroin (also known as skag, smack or dope) is generally grown in Asia and the Middle East.

The opium is extracted from ripening poppy pods after the flower has withered.

A milky liquid will ooze from the pod if it is cut and this liquid is collected and dried and is now crude opium.

From this mixture the painkillers morphine, codeine and heroin are extracted.

Heroin was traditionally injected into a vein, but because of the risk of contracting AIDS, intravenous use is now very rare. To shoot heroin, a user puts the powder in a spoon and, using a syringe, adds around .05 cubic centimetres of water. Vodka can also be used.

The spoon is then heated with a match, making the powder dissolve into a clear liquid which is drawn back into the syringe and injected right into a vein.

Because of the AIDS risk, most users now snort or sniff the drug.

If sprinkled on a marijuana cigarette, it is known as a fraggle joint.

Heroin has its origins in Southeast and Southwest Asia; Countries such as Thailand, Laos and Burma (which make up the so-called Golden Triangle) and Pakistan and Afghanistan.

Highly addictive, it dulls pain and depresses the central nervous system. Both the breathing and heart rate are slowed.

Symptoms of heroin use range from constipation and lethargy to drowsiness, euphoria, nausea and constricted pupils.

Convulsions, coma and death can result from an overdose. Withdrawal from heroin can lead a user to vomit, sweat profusely, experience chills, panic attacks and muscle and joint pain.