Three men who sold potentially deadly drugs on the dark web have been jailed.
Jake Levene, 22, Lee Childs, 45, and Mandy Christopher Lowther, 21, all from West Yorkshire, admitted supplying Fentanyl via an internet site.
The painkiller is 100 times more potent than morphine and has been linked to more than 125 deaths in the UK.
At Leeds Crown Court, Levene and Lowther were both jailed for 16 years and six months while Childs was jailed for 10 years and six months.
According to National Crime Agency (NCA) investigators, six of their 443 customers died from fentanyl-related deaths, although it could not be proved the final, lethal doses were supplied by the trio.
Charlie Livick, 33, who was one of those who died after taking the drug.
His mother Kathy Livick said: "I found my son dead and I resuscitated him for 30 minutes knowing he was dead. That's not something that you just get over."
The chemicals the trio dealt in were so strong that, one of them - Lowther - went into a coma, caused by a hypoxic brain injury, because of exposure to the drug.
The court heard the men made £163,474 in five months through the business which operated from an industrial unit in Peel Street in Morley.
They mixed the drugs with bulking agents and posted them to customers throughout the UK, as well as to the US, Canada, Australia, Argentina and Singapore.
Childs was captured on CCTV sending hundreds of drug packages from a post office.
Operating under the name UKBargins, the trio sold fentanyl, a prescription drug for severe pain relief, as well as carfentanyl, a more powerful variant which has no medical use for humans.
Prosecutors said more than 2,800 packages were sent by the trio plus at least 635g of pure carfentanyl.
An exact measurement of the quantity could not be provided as forensic scientist deemed the drug, which is used to put large animals to sleep, too dangerous to handle.
A raid on the premises by officers following the men's arrests in April 2017 is believed to be the largest seizure of the two drugs in Europe.
Inside, investigators found heavy duty gloves and two respirator masks, which the men wore to protect themselves while mixing and packaging the drugs.
Passing sentence, Judge Mushtaq Khokhar said: "This was a sophisticated operation. Small, I accept, but nevertheless sophisticated because one only has to look at what officers found when they raided the unit."
Graham Roberts, senior investigating officer from the NCA, said: "This wasn't Breaking Bad or a highly polished steel and clinical set up, it was pretty crude but highly effective."
All three men had previously pleaded guilty to two counts of supplying and two counts of exporting Class A drugs between December 2016 and April 2017.