Marcus Ekwubiri, Daniel McBride , Alexander Taff and Britney Salim all appeared at Sheffield Crown Court to stand trial, charged with various drug related offences.
All four entered guilty pleas and will be sentenced in August.
The four were arrested this time last year as part of an extensive, covert policing operation into drugs activity and organised crime in Sheffield.
Police executed six pre-planned warrants in the Manor, Darnall and Arbourthorne areas of the city on Thursday, June 9 2016, as two-months of planning for the operation, entitled Op Past, came to a head.
Just short of 6kg of class A and class B drugs were recovered from properties on Wulfric Road, Goore Avenue, Richmond Hall Road and Coleridge Gardens during the warrants, with an estimated street value of Â£159,000 as well as Â£3,000 in cash.
More than 2kg of heroin, with a value of approximately Â£110,000, almost 3.5kg of cannabis, worth around Â£39,000, 87g of cocaine, valued at roughly Â£9,000 and just under 10g of crack cocaine, priced approximately at Â£1,000, were all recovered
Ekwubiri, 30, of Wulfric Road, was charged with and pleaded guilty to three counts of possession with intent to supply class A drugs (cocaine, heroin and crack cocaine), possession with intent to class B drugs (cannabis) and possession of criminal property (Â£3,000 cash).
McBride, 34, of Goore Avenue, was charged with and pleaded guilty to possession with intent to supply class A drugs (heroin) and possession with intent to supply class B drugs (cannabis).
Taff, 22, of Goore Avenue, was charged with and pleaded guilty to possession with intent to supply class A drugs (cocaine) and Salim, 22, of Coleridge Gardens, was charged and pleaded guilty to allowing premises to be used for the supply of class A drugs (heroin).
The three men have been remanded into custody and Salim has been bailed until they are all due back in court to be sentenced in two months.
Detective Constable Paolo Messina leading the investigation said: “Since the warrants last year, there has been a vast amount of work undertaken to ensure a strong and practically indisputable case was built against these individuals, to evidence their involvement in drug dealing in our city.
“The recovery of the drugs is without a doubt a great result for our communities, as they are the cause of so much pain and suffering, however ensuring those involved in dealing the drugs are dealt with and brought to justice for their crimes is also an utmost priority.
“We will continue to conduct operations and investigate all aspects of organised crime and drugs activity in Sheffield, and I would encourage anyone who has any concerns or who has any information, to please come forward by calling 101, or anonymously making contact with Crimestoppers on 0800 555111.”