Arben Dumani, 23, and Gjeorgj Pjetri, 30, from Kosovo, and Albert Memia, 25, and Fabion Ponari, 23, of Albania, were found guilty at the High Court in Glasgow for processing and supplying the class A drug following a major police investigation.
Operation Eclipse saw officers from the Scottish Crime and Drug Enforcement Agency uncover a drugs "safe house" in Kinning Park, where the gang bulked up and remoulded cocaine blocks and pellets to deceive other dealers.
During a search of a property on May 30 last year officers found 2.1kg of cocaine and an industrial press with moulds for compressing blocks and pellets.
Weeks earlier, on May 11, they had watched as Dumani and Memia met Pjetri in a Glasgow car park, where a package was thrown from one car to the other.
Officers who later seized the parcel found 153g of cocaine.
During a later search of Dumani's home in Avonspark Street, Springburn, Ponari arrived carrying a large suitcase. It was later found to contain almost half a kilogram of cocaine and 10.15kg of creatine, a bulking agent.
Dumani was sentenced to 12 years, Memia received 10 years, Ponari got five years and Pjetri three years and six months.
Detective Chief Superintendent Athol Aitken, the unit's head of investigations, said: "The adulteration of drugs by drug dealers is commonplace and is a tactic used by serious organised crime groups to bulk out their products so they can increase their profit share.
"This is a case of dealers supplying to dealers and an unusual aspect of the investigation was the recovery of equipment used to compress the cocaine into pellets to deceive other drug dealers into believing it was of higher purity.
"This was a significant quantity of drugs that would have caused untold harm to Scottish communities.
"I welcome the court result, which will ensure the individuals involved are held accountable for their crimes."
